U.S. patent application number 13/243273 was filed with the patent office on 2012-10-11 for phosphor, method for producing phosphor, phosphor-containing composition, light-emitting device, lighting system and image display device.
This patent application is currently assigned to MITSUBISHI CHEMICAL CORPORATION. Invention is credited to Ryuji Adachi, Tatsuya Inoue, Naoto Kijima, Keiichi Seki, Takatoshi Seto, Hiroyasu Yamada.
Application Number | 20120256533 13/243273 |
Document ID | / |
Family ID | 42828350 |
Filed Date | 2012-10-11 |
United States Patent
Application |
20120256533 |
Kind Code |
A1 |
Seto; Takatoshi ; et
al. |
October 11, 2012 |
PHOSPHOR, METHOD FOR PRODUCING PHOSPHOR, PHOSPHOR-CONTAINING
COMPOSITION, LIGHT-EMITTING DEVICE, LIGHTING SYSTEM AND IMAGE
DISPLAY DEVICE
Abstract
To provide a yellow to orange phosphor which has high luminance
and excellent temperature characteristics and which also has high
luminance when mixed with a phosphor of a different color. A
phosphor containing a crystal phase represented by the following
formula [I], wherein when its object color is expressed by the
L*a*b* color system, the values of a*, b* and
(a*.sup.2+b*.sup.2).sup.1/2 satisfy -20.ltoreq.a*.ltoreq.-2,
71.ltoreq.b* and 71.ltoreq.(a*.sup.2+b*.sup.2).sup.1/2,
respectively:
R.sub.3-x-y-z+w2M.sub.zA.sub.1.5x+y-w2Si.sub.6-w1-w2Al.sub.w1+w2O.sub.y+-
w1N.sub.11-y-w1 [I]
Inventors: |
Seto; Takatoshi; (US)
; Kijima; Naoto; (US) ; Seki; Keiichi;
(US) ; Adachi; Ryuji; (US) ; Yamada;
Hiroyasu; (US) ; Inoue; Tatsuya; (US) |
Assignee: |
MITSUBISHI CHEMICAL
CORPORATION
Tokyo
JP
|
Family ID: |
42828350 |
Appl. No.: |
13/243273 |
Filed: |
September 23, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/JP10/55934 |
Mar 31, 2010 |
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13243273 |
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Current U.S.
Class: |
313/498 ;
252/301.4R; 252/301.6R |
Current CPC
Class: |
C09K 11/7734 20130101;
H05B 33/14 20130101; C04B 2235/445 20130101; C04B 2235/3895
20130101; H01L 2924/12044 20130101; H01L 2224/48091 20130101; C04B
35/6268 20130101; C09K 11/7766 20130101; H01L 33/504 20130101; C04B
2235/3227 20130101; C09K 11/7774 20130101; C09K 11/0883 20130101;
C04B 35/6262 20130101; H01L 2224/48091 20130101; C04B 2235/3215
20130101; C04B 35/597 20130101; C04B 2235/3225 20130101; C04B
2235/3224 20130101; C04B 2235/3229 20130101; C04B 2235/3206
20130101; C04B 2235/444 20130101; C09K 11/7706 20130101; C04B
35/62675 20130101; C04B 35/65 20130101; C04B 2235/40 20130101; C04B
2235/428 20130101; C04B 2235/3208 20130101; C04B 2235/401 20130101;
H01L 2924/00012 20130101; H01L 2924/00 20130101; H01L 2924/00014
20130101; C04B 35/62665 20130101; C04B 35/58085 20130101; C04B
2235/3891 20130101; H01L 2924/181 20130101; C04B 2235/5436
20130101; C04B 2235/3201 20130101; C04B 2235/3878 20130101; C04B
35/593 20130101; H01L 2224/48247 20130101; H01L 2924/181 20130101;
H01L 2924/12044 20130101 |
Class at
Publication: |
313/498 ;
252/301.4R; 252/301.6R |
International
Class: |
C09K 11/78 20060101
C09K011/78; H01J 1/63 20060101 H01J001/63 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2009 |
JP |
2009-086840 |
Oct 13, 2009 |
JP |
2009-236147 |
Claims
1. A phosphor containing a crystal phase represented by the
following formula [I], wherein when its object color is expressed
by the L*a*b* color system, the values of a*, b* and
(a*.sup.2+b*.sup.2).sup.1/2 satisfy -20.ltoreq.a*.ltoreq.-2,
71.ltoreq.b* and 71.ltoreq.(a*.sup.2+b*.sup.2).sup.1/2,
respectively:
R.sub.3-x-y-z+w2M.sub.zA.sub.1.5x+y-w2Si.sub.6-w1-w2Al.sub.w1+w2O.sub.y+w-
1N.sub.11-y-w1 [I] wherein R is at least one rare earth element
selected from the group consisting of La, Gd, Lu, Y and Sc; M is at
least one metal element selected from the group consisting of Ce,
Eu, Mn, Yb, Pr and Tb; A is at least one bivalent metal element
selected from the group consisting of Ba, Sr, Ca, Mg and Zn; and x,
y, z, w1 and w2 represent numerical values within the following
ranges, respectively: ( 1/7).ltoreq.(3-x-y-z+w2)/6<(1/2),
0.ltoreq.(1.5x+y-w2)/6<(9/2), 0.ltoreq.x<3, 0.ltoreq.y<2,
0<z<1, 0.ltoreq.w1.ltoreq.5, 0.ltoreq.w2.ltoreq.5,
0.ltoreq.w1+w2.ltoreq.5.
2. The phosphor according to claim 1, wherein
0<(1.5x+y-w2)/6<( 9/2).
3. The phosphor according to claim 1, wherein the values of b* and
(a*.sup.2+b*.sup.2).sup.1/2 satisfy 71.ltoreq.b*.ltoreq.105 and
71.ltoreq.(a*.sup.2+b*.sup.2).sup.1/2.ltoreq.105, respectively
4. The phosphor according to claim 1, wherein x is 0<x<3.
5. The phosphor according to claims 1, wherein
0.ltoreq.(1.5x+y-w2)<(9/2).
6. The phosphor according to claim 1, wherein the absorption
efficiency is at least 88%.
7. A method for producing a phosphor containing a crystal phase
represented by the following formula [I], which comprises nitriding
an alloy for production of a phosphor, containing at least elements
of R, A and Si, wherein said alloy is subjected to firing in the
presence of a flux:
R.sub.3-x-y-z+w2M.sub.zA.sub.1.5x+y-w2Si.sub.6-w1-w2Al.sub.w1+w2O.-
sub.y+w1N.sub.11-y-w1 [I] wherein R is at least one rare earth
element selected from the group consisting of La, Gd, Lu, Y and Sc;
M is at least one metal element selected from the group consisting
of Ce, Eu, Mn, Yb, Pr and Tb; A is at least one bivalent metal
element selected from the group consisting of Ba, Sr, Ca, Mg and
Zn; and x, y, z, w1 and w2 represent numerical values within the
following ranges, respectively: (
1/7).ltoreq.(3-x-y-z+w2)/6<(1/2),
0.ltoreq.(1.5x+y-w2)/6<(9/2), 0.ltoreq.x<3, 0.ltoreq.y<2,
0<z<1, 0.ltoreq.w1.ltoreq.5, 0.ltoreq.w2.ltoreq.5,
0.ltoreq.w1+w2.ltoreq.5.
8. The method for producing a phosphor according to claim 7,
wherein 0<(1.5x+y-w2)/6<(9/2).
9. The method for producing a phosphor according to claim 7,
wherein 0.ltoreq.(1.5x+y-w2)<(9/2).
10. The method for producing a phosphor according to claim 7,
wherein the firing is carried out under a temperature condition
such that the rate of temperature rise during the firing is at most
0.5.degree. C./min within a temperature range corresponding to at
least a part of the low temperature side of an exothermic peak
obtainable by TG-DTA (Thermogravimetry/Differential Thermal
Analysis) during the nitriding reaction of the alloy for production
of a phosphor.
11. The method for producing a phosphor according to claim 7,
wherein the firing is carried out in a hydrogen-containing nitrogen
gas atmosphere.
12. The method for producing a phosphor according to claim 7,
wherein after the firing, the obtained fired product is washed with
an acidic aqueous solution.
13. A phosphor containing a composition represented by the
following formula [I], wherein when its object color is expressed
by the L*a*b* color system, the values of a*, b* and
(a*.sup.2+b*.sup.2).sup.1/2 satisfy -20.ltoreq.a*.ltoreq.-2,
71.ltoreq.b* and 71.ltoreq.(a*.sup.2+b*.sup.2).sup.1/2,
respectively: (Ln,Ca,Ce).sub.3+.alpha.Si.sub.6N.sub.11 [I'] wherein
Ln is at least one rare earth element selected from the group
consisting of La, Gd, Lu, Y and Sc, and .alpha. is a numerical
value within a range of -0.1.ltoreq..alpha..ltoreq.1.5.
14. A phosphor-containing composition comprising the phosphor as
defined in claim 1 and a liquid medium.
15. A light-emitting device having a first illuminant and a second
illuminant which emits visible light under irradiation with light
from the first illuminant, wherein the second illuminant contains,
as a first phosphor, at least one phosphor selected from the group
consisting of the phosphor as defined in claim 1.
16. The light-emitting device according to claim 15, wherein the
first phosphor has an emission peak wavelength within a wavelength
range of from 420 nm to 450 nm.
17. The light-emitting device according to claim 15, wherein the
second illuminant contains, as a second phosphor, at least one
phosphor different in the emission peak wavelength from the first
phosphor.
18. The light-emitting device according to claim 15, wherein the
first phosphor has an emission peak within a wavelength range of
from 420 nm to 500 nm, and the second illuminant contains, as a
second phosphor, at least one phosphor having an emission peak
within a wavelength range of from 565 nm to 780 nm.
19. The light-emitting device according to claim 15, wherein the
first phosphor has an emission peak within a wavelength range of
from 300 nm to 420 nm, and the second illuminant contains, as a
second phosphor, at least one phosphor having an emission peak
within a wavelength range of from 420 nm to 500 nm.
20. The light-emitting device according to claim 15, wherein the
first phosphor has an emission peak within a wavelength range of
from 300 nm to 420 nm, and the second illuminant contains, as a
second phosphor, at least one phosphor having an emission peak
within a wavelength range of from 420 nm to 500 nm, at least one
phosphor having an emission peak within a wavelength range of from
500 nm to 550 nm, and at least one phosphor having an emission peak
within a wavelength range of from 565 nm to 780 nm.
21. A lighting system provided with the light-emitting device as
defined in claim 15.
22. An image display device provided with the light-emitting device
as defined in claim 15.
Description
TECHNICAL FIELD
[0001] The present invention relates to a phosphor comprising a
nitrogen-containing compound such as a composite nitride or
oxynitride, a method for producing it, a phosphor-containing
composition which contains such a phosphor, a light-emitting device
employing such a phosphor, and an image display device and lighting
system provided with such a light-emitting device. More
specifically, the present invention relates to a phosphor which
emits a yellow to orange light under irradiation with light from an
excitation light source such as a semiconductor light-emitting
element being a first illuminant, a method for its production, a
phosphor-containing composition which contains such a phosphor, a
light-emitting device with high efficiency employing such a
phosphor, and an image display device and lighting system provided
with such a light-emitting device.
BACKGROUND ART
[0002] In recent years, a semiconductor light-emitting device (LED
light-emitting device) having a light source such as a
light-emitting diode (hereinafter referred to as "LED") and a
phosphor combined, has been practically used. Particularly, a
light-emitting device having blue LED and a cerium-activated
yttrium/aluminum/garnet type yellow phosphor combined is well used
as a white-emitting device, and from such a viewpoint, a demand for
a yellow phosphor is very high.
[0003] Accordingly, a research has been active for a novel yellow
phosphor different from a conventional cerium-activated
yttrium/aluminum/garnet type phosphor, and it is known that a
nitride phosphor as disclosed in Patent Document 1 or 2 is
particularly superior in color rendering properties to the
cerium-activated yttrium/aluminum/garnet type phosphor.
PRIOR ART DOCUMENTS
Patent Documents
[0004] Patent Document 1: JP-A-2008-088362 [0005] Patent Document
2: WO2008/132954
DISCLOSURE OF INVENTION
Technical Problem
[0006] However, in the market of light-emitting devices as
described above, development of products having higher performance
is always desired.
[0007] The present invention has been made under such
circumstances, and it is a first object of the present invention to
obtain a phosphor having a higher light-emitting efficiency when
applied to a LED light-emitting device, with respect to the
above-mentioned nitride type yellow phosphor. Further, another
object of the present invention is to provide a method for
producing such a phosphor, a phosphor-containing composition and a
light-emitting device employing such as phosphor, and a lighting
system and image display device provided with such a light-emitting
device.
Solution to Problem
[0008] The present inventors have conducted an extensive study to
solve the above problem and as a result, have found that when a
phosphor wherein when its object color is expressed by the L*a*b*
color system, the values of a*, b* and (a*.sup.2+b*.sup.2).sup.1/2
are within certain specific ranges, is used for a light-emitting
device, the pseudo white color emission will be excellent, and the
color emission-efficiency will be high. The present invention has
been accomplished on the basis of these discoveries.
[0009] That is, the present invention provides the following (1) to
(22).
(1) A phosphor containing a crystal phase represented by the
following formula [I], wherein when its object color is expressed
by the L*a*b* color system, the values of a*, b* and
(a*.sup.2+b*.sup.2).sup.1/2 satisfy -20.ltoreq.a*.ltoreq.-2,
71.ltoreq.b* and 71.ltoreq.(a*.sup.2+b*.sup.2).sup.1/2,
respectively:
R.sub.3-x-y-z+w2M.sub.zA.sub.1.5x+y-w2Si.sub.6-w1-w2Al.sub.w1+w2O.sub.y+-
w1N.sub.11-y-w1 [I]
wherein R is at least one rare earth element selected from the
group consisting of La, Gd, Lu, Y and Sc; M is at least one metal
element selected from the group consisting of Ce, Eu, Mn, Yb, Pr
and Tb; A is at least one bivalent metal element selected from the
group consisting of Ba, Sr, Ca, Mg and Zn; and x, y, z, w1 and w2
represent numerical values within the following ranges,
respectively:
( 1/7).ltoreq.(3-x-y-z+w2)/6<(1/2),
0.ltoreq.(1.5x+y-w2)/6<(9/2),
0.ltoreq.x<3,
0.ltoreq.y<2,
0<z<1,
0.ltoreq.w1.ltoreq.5,
0.ltoreq.w2.ltoreq.5,
0.ltoreq.w1+w2.ltoreq.5.
(2) The phosphor according to the above (1), wherein
0<(1.5x+y-w2)/6<(9/2). (3) The phosphor according to the
above (1) or (2), wherein the values of b* and
(a*.sup.2+b*.sup.2).sup.1/2 satisfy 71.ltoreq.b*.ltoreq.105 and
71.ltoreq.(a*.sup.2+b*.sup.2).sup.1/2.ltoreq.105, respectively (4)
The phosphor according to any one of the above (1) to (3), wherein
x is 0<x<3. (5) The phosphor according to any one of the
above (1), (3) and (4), wherein 0.ltoreq.(1.5x+y-w2)<(9/2). (6)
The phosphor according to any one of above (1) to (5), wherein the
absorption efficiency is at least 88%. (7) A method for producing a
phosphor containing a crystal phase represented by the following
formula [I], which comprises nitriding an alloy for production of a
phosphor, containing at least elements of R, A and Si, wherein said
alloy is subjected to firing in the presence of a flux:
R.sub.3-x-y-z+w2M.sub.zA.sub.1.5x+y-w2Si.sub.6-w1-w2Al.sub.w1+w2O.sub.y+-
w1N.sub.11-y-w1 [I]
wherein R is at least one rare earth element selected from the
group consisting of La, Gd, Lu, Y and Sc; M is at least one metal
element selected from the group consisting of Ce, Eu, Mn, Yb, Pr
and Tb; A is at least one bivalent metal element selected from the
group consisting of Ba, Sr, Ca, Mg and Zn; and x, y, z, w1 and w2
represent numerical values within the following ranges,
respectively:
( 1/7).ltoreq.(3-x-y-z+w2)/6<(1/2),
0.ltoreq.(1.5x+y-w2)/6<(9/2),
0.ltoreq.x<3,
0.ltoreq.y<2,
0<z<1,
0.ltoreq.w1.ltoreq.5,
0.ltoreq.w2.ltoreq.5,
0.ltoreq.w1+w2.ltoreq.5.
(8) The method for producing a phosphor according to the above (7),
wherein 0<(1.5x+y-w2)/6<(9/2). (9) The method for producing a
phosphor according to above (7), wherein
0.ltoreq.(1.5x+y-w2)<(9/2). (10) The method for producing a
phosphor according to any one of above (7) to (9), wherein the
firing is carried out under a temperature condition such that the
rate of temperature rise during the firing is at most 0.5.degree.
C./min within a temperature range corresponding to at least a part
of the low temperature side of an exothermic peak obtainable by
TG-DTA (thermogravimetry/differential thermal analysis) during the
nitriding reaction of the alloy for production of a phosphor. (11)
The method for producing a phosphor according to any one of above
(7) to (10), wherein the firing is carried out in a
hydrogen-containing nitrogen gas atmosphere. (12) The method for
producing a phosphor according to any one of above (7) to (11),
wherein after the firing, the obtained fired product is washed with
an acidic aqueous solution. (13) A phosphor containing a
composition represented by the following formula [I'], wherein when
its object color is expressed by the L*a*b* color system, the
values of a*, b* and (a*.sup.2+b*.sup.2).sup.1/2 satisfy
-20.ltoreq.a*.ltoreq.-2, 71.ltoreq.b* and
71.ltoreq.(a*.sup.2+b*.sup.2) respectively:
(Ln,Ca,Ce).sub.3+.alpha.Si.sub.6N.sub.11 [I']
wherein Ln is at least one rare earth element selected from the
group consisting of La, Gd, Lu, Y and Sc, and .alpha. is a
numerical value within a range of -0.1.ltoreq..alpha..ltoreq.1.5.
(14) A phosphor-containing composition comprising the phosphor as
defined in any one of the above (1) to (6) and a liquid medium.
(15) A light-emitting device having a first illuminant and a second
illuminant which emits visible light under irradiation with light
from the first illuminant, wherein the second illuminant contains,
as a first phosphor, at least one phosphor selected from the group
consisting of the phosphor as defined in any one of the above (1)
to (6). (16) The light-emitting device according to the above (15),
wherein the first phosphor has an emission peak wavelength within a
wavelength range of from 420 nm to 450 nm. (17) The light-emitting
device according to the above (15) or (16), wherein the second
illuminant contains, as a second phosphor, at least one phosphor
different in the emission peak wavelength from the first phosphor.
(18) The light-emitting device according to the above (15), wherein
the first phosphor has an emission peak within a wavelength range
of from 420 nm to 500 nm, and the second illuminant contains, as a
second phosphor, at least one phosphor having an emission peak
within a wavelength range of from 565 nm to 780 nm. (19) The
light-emitting device according to the above (15), wherein the
first phosphor has an emission peak within a wavelength range of
from 300 nm to 420 nm, and the second illuminant contains, as a
second phosphor, at least one phosphor having an emission peak
within a wavelength range of from 420 nm to 500 nm. (20) The
light-emitting device according to the above (15), wherein the
first phosphor has an emission peak within a wavelength range of
from 300 nm to 420 nm, and the second illuminant contains, as a
second phosphor, at least one phosphor having an emission peak
within a wavelength range of from 420 nm to 500 nm, at least one
phosphor having an emission peak within a wavelength range of from
500 nm to 550 nm, and at least one phosphor having an emission peak
within a wavelength range of from 565 nm to 780 nm. (21) A lighting
system provided with the light-emitting device as defined in any of
the above (15) to (20). (22) An image display device provided with
the light-emitting device as defined in any one of the above (15)
to (20).
Advantageous Effects of Invention
[0010] According to the present invention, it is possible to
provided a yellow nitride phosphor which is superior in the pseudo
white color to the conventional one and which has high luminance or
luminous efficiency, when used for a light-emitting device. By
using such a phosphor, it is possible to realize a
phosphor-containing composition, a light-emitting device with high
efficiency, a lighting system and a image display device.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a diagrammatical perspective view illustrating the
positional relation between an excitation light source (first
illuminant) and a phosphor-containing portion (second illuminant)
in one embodiment of the light-emitting device of the present
invention.
[0012] Each of FIGS. 2(a) and 2(b) is a diagrammatical
cross-sectional view illustrating an embodiment of a light-emitting
device having an excitation light source (first illuminant) and a
phosphor-containing portion (second illuminant).
[0013] FIG. 3 is a diagrammatical cross-sectional view illustrating
an embodiment of the lighting system of the present invention.
[0014] FIG. 4 is the powder X-ray diffraction pattern of the
phosphor produced in Example A1.
[0015] FIG. 5 is the powder X-ray diffraction pattern of the
phosphor produced in Example A7.
DESCRIPTION OF EMBODIMENTS
[0016] Now, the present invention will be described with reference
to its embodiments or exemplifications. However, it should be
understood that the present invention is by no means restricted to
the following embodiments or exemplifications and may be carried
out as optionally changed or modified within a range not to depart
from the gist of the present invention. In this specification, the
numerical-range represented by means of "-" or "to" means the range
containing the numerical values given before and after "-" or "to"
as the lower and upper limit values. Further, in this
specification, the relations between colors and color coordinates
are all based on JIS standards (JIS Z8110).
[0017] Further, in the compositional formulae of phosphors in this
specification, the adjacent compositional formulae are delimited by
a comma ",". Further, plural elements being comma-delimited means
that one or more of such elements may be contained in any optional
combination and composition. For example, a compositional formula
"(Ba,Sr,Ca)Al.sub.2O.sub.4:Eu" comprehensively represents all of
"BaAl.sub.2O.sub.4:Eu", "SrAl.sub.2O.sub.4:Eu",
"CaAl.sub.2O.sub.4:Eu", "Ba.sub.1-xSr.sub.xAl.sub.2O.sub.4:Eu",
"Ba.sub.1-xCa.sub.xAl.sub.2O.sub.4:Eu",
"Sr.sub.1-xCa.sub.xAl.sub.2O.sub.4:Eu" and
"Ba.sub.1-x-ySr.sub.xCa.sub.yAl.sub.2O.sub.4:Eu" (provided that in
the above formulae, 0<x<1, 0<y<1, 0<x+y<1).
[1. Phosphor of the Present Invention]
[0018] As mentioned above, the phosphor of the present invention is
a phosphor containing a crystal phase represented by the formula
[I]:
R.sub.3-x-y-z+w2M.sub.zA.sub.1.5x+y-w2Si.sub.6-w1-w2Al.sub.w1+w2O.sub.y+-
w1N.sub.11-y-w1 [I]
wherein R is at least one rare earth element selected from the
group consisting of La, Gd, Lu, Y and Sc; M is at least one metal
element selected from the group consisting of Ce, Eu, Mn, Yb, Pr
and Tb; A is at least one bivalent metal element selected from the
group consisting of Ba, Sr, Ca, Mg and Zn; and x, y, z, w1 and w2
represent numerical values within the following ranges,
respectively:
( 1/7).ltoreq.(3-x-y-z+w2)/6<(1/2),
0.ltoreq.(1.5x+y-w2)/6<(9/2),
0.ltoreq.x<3,
0.ltoreq.y<2,
0<z<1,
0.ltoreq.w1.ltoreq.5,
0.ltoreq.w2.ltoreq.5,
0.ltoreq.w1+w2.ltoreq.5.
wherein when its object color is expressed by the L*a*b* color
system, the values of a*, b* and (a*.sup.2+b*.sup.2).sup.1/2
satisfy -20.ltoreq.a*.ltoreq.-2, 71.ltoreq.b* and
71.ltoreq.(a*.sup.2+b*.sup.2).sup.1/2, respectively.
[0019] In the following, firstly, the crystal phase represented by
the formula [I] will be described in more detail.
[1-1. Composition of Crystal Phase of the Phosphor of the Present
Invention]
[0020] In the above formula [I], R is at least one rare earth
element selected from the group consisting of La, Gd, Lu, Y and Sc.
Among them, R is preferably at least one rare earth element
selected from the group consisting of La, Gd and Y. Among them, R
is more preferably at least one rare earth element selected from
the group consisting of La and Gd. Among them, it is particularly
preferably La.
[0021] Further, as R, one rare earth element may be used alone, or
two or more rare earth elements may be used in an optional
combination and ratio. By using two or more rare earth elements as
R, it is possible to change the excitation wavelength or emission
wavelength of the phosphor of the present invention thereby to
adjust the CIE chromaticity coordinate (x,y).
[0022] However, in a case where R is composed of two or more
elements, the proportion of La, a mixture of La and Gd, or a
mixture of La, Gd and Y, in R is usually preferably at least 70 mol
%, more preferably at least 80 mol %, particularly preferably at
least 95 mol %, whereby it is possible to improve the luminance or
emission intensity. Further, from the viewpoint of the luminance or
emission intensity, the proportion of La based on the total amount
of La, Gd and Y is usually preferably at least 70 mol %, more
preferably at least 80 mol %, particularly preferably at least 95
mol %. Further, the proportion of the total amount of Gd and Y
based on the total amount of La, Gd and Y is usually preferably
from 3 to 20 mol %, more preferably from 5 to 15 mol %, from the
viewpoint of good color of yellow as the emission color.
[0023] In the above formula [I], M is at least one metal element
selected from the group consisting of Ce, Eu, Mn, Yb, Pr and Tb.
Here, M is one to function as an activation element. Further, as M,
among the above metal elements, only one type may be used, or two
or more types may be used in combination in an optional combination
and ratio. Among them, M is preferably one containing at least Ce
from the viewpoint of the luminous efficiency and emission peak
wavelength, and it is more preferred to use only Ce.
[0024] With respect to Ce as an activation element, at least a part
thereof will be present in the form of a trivalent cation in the
phosphor of the present invention. At that time, activation element
Ce may take trivalent or tetravalent valency, but the proportion of
the trivalent cation should better be high. Specifically, the
proportion of Ce.sup.3+ based on the entire Ce amount is usually at
least 20 mol %, preferably at least 50 mol %, more preferably at
least 80 mol %, particularly preferably at least 90 mol %, most
preferably 100 mol %.
[0025] Further, with respect to Eu, Mn, Yb, Pr and Tb as activation
elements other than Ce, there may be a case where cations different
in the valency coexist like in the case of Ce. By an addition of a
very small amount of such elements, there may be a case where a
sensitizing effect is obtainable, and the luminance will be
improved.
[0026] Here, the proportion of Ce.sup.3+ in the entire Ce contained
in the phosphor of the present invention can be obtained by e.g.
the measurement of X-ray Absorption Fine Structure. That is, when
L3 absorption edges of Ce atoms are measured, Ce.sup.3+ and
Ce.sup.4+ exhibit separate absorption peaks, and their ratio can be
quantified from their areas. Further, the proportion of Ce.sup.3+
in the entire Ce contained in the phosphor of the present invention
can be obtained also by measurement of electron spin resonance
(ESR). Further, with respect to the above M, the amount of the atom
with the desired valency can be measured by the measurement of
X-ray Absorption Fine Structure like in the case of Ce.
[0027] In the above formula [I], A is at least one bivalent metal
element selected from the group consisting of Ba, Sr, Ca, Mg and
Zn. At that time, A is preferably at least one bivalent metal
element selected from the group consisting of Sr, Ca and Mg, more
preferably Ca and Mg, further preferably Ca. Further, as the above
A, only one of such elements may be used, or two or more of them
may be used in an optional combination and ratio.
[0028] The basic system of the crystal phase represented by the
above formula [I] is a system wherein R and A coexist as surrounded
by a SiN.sub.4 tetrahedron. In the crystal phase represented by the
formula [I], it is possible to increase bivalent A, while
decreasing trivalent R (hereinafter this substitution will be
referred to as "R-A substitution"). This represents a unique
crystal phase, wherein the increase of A does not correspond to the
decrease of R, but the increase of A takes place 1.5 times the
reduction of R, whereby charge compensation is carried out.
[0029] Further, in the phosphor of the present invention, a part of
R may be substituted by A by a system other than the above R-A
substitution, and in such a case, N anions are substituted by O
anions by the number of substituted R.
[0030] Further, in the above basic system of the crystal phase, a
part of Si may be substituted by Al. For this purpose, Al appears
in the formula [I]. In such a case, N anions are substituted by O
anions, and/or bivalent A is substituted by trivalent R.
[0031] In the above formula [I], 1.5.times. is a numerical value
representing the amount of A substituted for a part of R by the
above R-A substitution. If the value x at the time of charging
before the firing is too small, a byproduct is likely to be formed
during the firing. However, this value x gradually decreases during
the firing, and the final value x in the phosphor should better be
small with a view to letting the phosphor undergo crystal growth to
obtain high luminance. The value x at that time is usually at most
2.5, preferably at most 2.2, more preferably at most 1.5, in the
case of utilizing a yellow emission containing a reddish component.
On the other hand, in the case of utilizing the yellow emission
itself, it is usually at most 1.5, preferably at most 1.0, more
preferably at most 0.5, further preferably at most 0.2. The lower
limit of the value x may be 0 or a value exceeding 0.
[0032] In the above formula [I], y is a numerical value
representing the amount of A substituted for a part of R in a
system other than the above R-A substitution. While oxygen to be
included should better be less, there may be a case oxygen will be
included slightly from the raw material or during the firing. In
such a case, N anions in the phosphor are substituted by O anions,
and for the charge compensation, substitution of A will be
required. The value y may include 0, but is usually larger than 0,
preferably at least 0.002, more preferably at least 0.005, further
preferably at least 0.008, and in the case of utilizing a yellow
emission containing a reddish component, it is usually at most 2.5,
preferably at most 2.2, more preferably at most 1.5. On the other
hand, in the case of utilizing the yellow emission itself, it is
usually at most 1.5, preferably at most 1.0, more preferably at
most 0.5, further preferably at most 0.2.
[0033] In the above formula [I], z is a numerical value
representing the amount of activation element M and is usually
larger than 0, preferably at least 0.002, more preferably at least
0.01, further preferably at least 0.05, and usually less than 1,
preferably at most 0.7, more preferably at most 0.6. If the value z
is too large, it is possible that the emission intensity decreases
due to concentration quenching.
[0034] In the above formula [I], the substitution number of moles
of Al is represented by w1 and w2. The range of this w1 is usually
at least 0, preferably at least 0.002, more preferably at least
0005 and usually at most 5, preferably at most 2, more preferably
at most 1, further preferably at most 0.5. On the other hand, the
range of w2 is usually at least 0, preferably at least 0.002 and
usually at most 5, preferably at most 2, more preferably at most 1,
further preferably at most 0.5. By the substitution of Al, it is
possible to adjust the color tone of the emission color of the
phosphor of the present invention. Further, by adjusting w1 and w2
to be within the above ranges, it is possible to adjust the
emission color while maintaining the crystal structure.
[0035] Further, in the above formula [I], the above-mentioned x, y
and z satisfy the relations of the following two relations. (
1/7).ltoreq.(3-x-y-z+w2)/6<(1/2), and
0.ltoreq.(1.5x+y-w2)/6<( 9/2).
[0036] That is, in the formula [I], "(3-x-y-z+w2)/6" represents a
numerical value of at least 1/7 and less than 1/2.
[0037] Further, in the formula [I], "(1.5x+y-w2)/6" represents a
numerical value of at least 0 and less than 9/2. And, more
preferably, it is larger than 1.
[0038] Further, from the viewpoint of the emission intensity, the
number of moles of oxygen (y+w1) in the formula [I], is preferably
less than 2, more preferably less than 1.7, further preferably less
than 1.5. Further, from the viewpoint of production efficiency, the
above number of moles of oxygen (y+w1) is preferably at least 0.01,
more preferably at least 0.04.
[0039] Further, from the viewpoint of the emission intensity, the
number of moles of Al (w1+w2) in the formula [I] is usually at most
5, preferably at most 3, more preferably at most 1. On the other
hand, the lower limit is preferably close to 0, particularly
preferably 0, from the viewpoint of the production efficiency.
[0040] The phosphor of the present invention shows a good
performance even when it has an anion or cation deficiency to some
extent. The formula [I] is a usual formula assumed to be free from
a cation deficiency or an anion deficiency. Therefore, when a
deficiency is formed, there may be a case where x, y, z, w1 and w2
cannot be determined from the actual elemental analytical
values.
[0041] Further, in a case where the phosphor of the present
invention is to be actually analyzed, the coefficients of the
respective elements are likely to include measurement errors, and
there may be a case where it is difficult to separate oxygen or
nitrogen adsorbed on the surface or a small amount of impurities,
and thus, it is needless to say that in reality, the values of x,
y, z, w1 and w2 have allowable ranges to some extent.
[0042] Further, the phosphor of the present invention is
particularly preferably a phosphor containing a composition
represented by the following formula [I'], wherein when its object
color is expressed by the L*a*b* color system, the values of a*, b*
and (a*.sup.2+b*.sup.2).sup.1/2 satisfy -20.ltoreq.a*.ltoreq.-2,
71.ltoreq.b* and 71.ltoreq.(a*.sup.2+b*.sup.2).sup.1/2,
respectively:
(Ln,Ca,Ce).sub.3+.alpha.Si.sub.6N.sub.11 [I']
wherein Ln is at least one rare earth element selected from the
group consisting of La, Gd, Lu, Y and Sc, and .alpha. is a
numerical value within a range of
-0.1.ltoreq..alpha..ltoreq.1.5.
[0043] Such a phosphor of the formula [I'] is essentially the same
as the phosphor of the formula [I], however, in order to avoid
formation of anion deficiency or cation deficiency or as mentioned
above, in the case of actually analyzing an obtained phosphor, in
order to avoid an analytical error or formation of an impurity
phase with a composition other than the present invention in the
formed phosphor or in order to intentionally avoid an influence of
an impurity element, including the case of adjusting the total
amount of Ln, Ca and Ce which is essentially required, in a typical
phosphor of the present invention, the composition within a range
of the total amount of Ln, Ca and Ce allowable as the entire
phosphor is defined. In such a case, -0.1.ltoreq..alpha..ltoreq.1.5
is preferred, and more preferred is -0.1.ltoreq..alpha..ltoreq.1.0.
Especially in a case where the luminance is to be improved,
-0.1.ltoreq..alpha..ltoreq.0.1 is particularly preferred.
[0044] In the phosphor of the formula [I'], the amount of N may
sometimes change to some extent for such a reason as e.g. cation
deficiency or anion deficiency. When such an allowable range is
represented by .beta., the coefficient of N becomes 11+.beta.. At
that time, a range of -0.2.ltoreq..beta..ltoreq.0.5 is preferred,
and more preferred is 0.ltoreq..beta..ltoreq.0.3, and further
preferred is 0.ltoreq..beta..ltoreq.0.1. The above numerical values
are numerical values when the molar ratio of Si is set to be 6.
Further, when Si is set to be 6 mol, oxygen may be contained in an
amount of at most 1 mol, more preferably at most 0.5 mol, further
preferably at most 0.3 mol, particularly preferably at most 0.1
mol, in addition to the formula [I']. Here, from the viewpoint of
the analysis, oxygen is considered to be one contained in the
phosphor and one adsorbed on the surface or interior of the
phosphor or present separately from the crystals. From the
viewpoint of the luminance, in the formula [I'], the amount of Ca
is preferably less than 2 mol, more preferably less than 1 mol,
further preferably less than 0.5 mol, most preferably less than 0.2
mol. In addition to the above-mentioned adjustment of the emission
color by e.g. Gd or Y, it is possible to adjust the emission color
also by the number of moles of Ca, from yellow slightly close to
green, to orange, within a range of from 0 to 0.5 mol.
[0045] Within the chemical composition of the above formula [I],
preferred specific examples will be given below, but it should be
understood that the composition of the crystal phase of the
phosphor of the present invention is by no means limited to the
following examples. Within the chemical composition of the formula
[I], preferred examples having no oxygen included, include the
following. La.sub.1.37Ce.sub.0.03Ca.sub.2.40Si.sub.6N.sub.11,
La.sub.2.15Ce.sub.0.10Ca.sub.1.23Si.sub.6N.sub.11,
La.sub.2.57Ce.sub.0.03Ca.sub.0.60Si.sub.6N.sub.11,
La.sub.1.17Ce.sub.0.03Ca.sub.2.70Si.sub.6N.sub.11,
La.sub.2.68Ce.sub.0.30Ca.sub.0.03Si.sub.6N.sub.11,
La.sub.2.74Ce.sub.0.20Ca.sub.0.09Si.sub.6N.sub.11,
La.sub.2.50Ce.sub.0.30Ca.sub.0.30Si.sub.6N.sub.11,
La.sub.2.70Ce.sub.0.30Si.sub.6N.sub.11,
La.sub.2.5Gd.sub.0.20Ce.sub.0.30Si.sub.6N.sub.11,
La.sub.2.3Gd.sub.0.40Ce.sub.0.30Si.sub.6N.sub.11,
La.sub.2.49Gd.sub.0.15Ce.sub.0.30Ca.sub.0.09Si.sub.6N.sub.11,
La.sub.2.5Y.sub.0.20Ce.sub.0.30Si.sub.6N.sub.11,
La.sub.2.67Ce.sub.0.03Ca.sub.0.45Si.sub.6N.sub.11,
La.sub.2.60Ce.sub.0.10Ca.sub.0.45Si.sub.6N.sub.11. [0046] Further,
preferred examples wherein oxygen is present, include the
following.
La.sub.1.71Ce.sub.0.10Ca.sub.1.57Si.sub.6O.sub.0.44N.sub.10.56,
La.sub.1.17Ce.sub.0.03Ca.sub.2.20Si.sub.6O.sub.1.00N.sub.10.00,
La.sub.2.37Ce.sub.0.03Ca.sub.0.75Si.sub.6O.sub.0.30N.sub.10.70,
La.sub.2.68Ce.sub.0.30Ca.sub.0.02Si.sub.6O.sub.0.02N.sub.10.98,
La.sub.2.74Ce.sub.0.20Ca.sub.0.15Si.sub.6O.sub.0.06N.sub.10.94,
La.sub.2.50Ce.sub.0.30Ca.sub.0.20Si.sub.6O.sub.0.20N.sub.10.80,
La.sub.2.49Ce.sub.0.30Ca.sub.0.30Si.sub.6O.sub.0.03N.sub.10.57,
La.sub.1.25Ce.sub.0.25Ca.sub.2.20Si.sub.6O.sub.0.10N.sub.10,
La.sub.2.66Ce.sub.0.20Ca.sub.0.15Si.sub.6O.sub.0.12N.sub.10.88,
La.sub.2.61Ce.sub.0.30Ca.sub.0.09Si.sub.6O.sub.0.09N.sub.10.91,
La.sub.2.57Gd.sub.0.15Ce.sub.0.25Ca.sub.0.03Si.sub.6O.sub.0.03N.sub.10.97-
.
[0047] Further, a crystal phase wherein oxygen is present in a
small amount, and no Ca is present, is also mentioned as preferred.
In such a case, the crystal phase will be one wherein a very small
portion of La or Si is deficient.
[0048] The above-described crystal phase represented by the formula
[I] is essentially the one constituting a new structure (space
group and site-constituting ratio) in an alkaline earth metal
element-rare earth element (Ln)-Si--N system. Now, the difference
between this crystal phase and the crystal phases of known
substances will be described.
[0049] The space group of the crystal phase represented by the
above formula [I] is P4bm or its analogous space group, while the
space group of known SrYbSi.sub.4N.sub.7 or BaYbSi.sub.4N.sub.7 is
P6.sub.3mc (Zeitschrift fur Anorganische and Allgemeine Chemie,
1997, vol. 623, p. 212), and the space group of known BaEu
(Ba.sub.0.5Eu.sub.0.5)YbSi.sub.6N.sub.11 is P2.sub.13 (H. Huppertz,
Doctoral thesis, Bayreuth University, 1997). Thus, the crystal
phase represented by the formula [I] is substantially different in
the space group from the known phosphors. Further, the crystal
phase represented by the formula [I] is substantially different
from the known phosphors in the powder X-ray diffraction pattern
constituting its base, and it is therefore apparent that the
crystal structure is different.
[0050] The crystal phase represented by the above formula [I] has a
unique site-constituting ratio such that the total number of
cations having a lower valency than Si surrounded by SiN.sub.4
tetrahedrons exceeds 3/6 to the number of SiN.sub.4 tetrahedrons.
On the other hand, in the known Ce-activated
La.sub.3Si.sub.6N.sub.11, the total number of cations having a
lower valency than Si surrounded by SiN.sub.4 tetrahedrons is
exactly 3/6 to the number of SiN.sub.4 tetrahedrons
(JP-A-2003-206481), and in the known
LnAl(Si.sub.6-zAl.sub.z)N.sub.10-zO.sub.z:Ce phosphor, the total
number of cations having a lower valency than Si surrounded by
Si(or Al)N(or O).sub.4 tetrahedrons is 2/6 to the number of Si(or
Al)N(or O).sub.4 tetrahedrons (Patent Document 1). Thus, the
crystal phase represented by the formula [I] is apparently
different from the known phosphors in the constituting ratio of
each site characterizing the structure.
[0051] Further, in the phosphor of the present invention, a part of
the constituting elements of the crystal phase represented by the
above formula [I] may be deficient or may be substituted by other
atoms, so long as the performance is not impaired. The following
may be mentioned as examples of such other elements.
[0052] For example, in the formula [I], at the position of M, at
least one transition metal element or rare earth element selected
from the group consisting of Nd, Sm, Dy, Ho, Er and Tm may be
substituted. Among them, it is preferred that Sm and/or Tm as a
rare earth element is substituted.
[0053] Further, for example, in the formula [I], all or a part of
Al may be replaced by B. In a case where raw materials are put into
a BN container, followed by firing to produce a phosphor of the
present invention, B will be included in the obtainable phosphor,
and it is possible to produce a phosphor wherein Al is replaced by
B as mentioned above. Further, for example, in the formula [I], at
the positions of O and/or N, anions such as S, Cl and/or F may be
substituted.
[0054] Further, in the formula [I], a part of Si may be replaced by
Ge and/or C. Such a substitution ratio is preferably at most 10 mol
%, more preferably at most 5 mol %, further preferably 0 mol %.
Further, for such a reason that no substantial reduction of the
emission strength is brought about, at each site of R, A, Si, Al O
and N in the formula [I], at most 5 mol % of an element may be
substituted, or at each site, at most 10 mol % of deficiency may be
formed. However, both of such substitution and deficiency should
better be 0 mol %.
[0055] However, in order to obtain the merits of the present
invention distinctly, it is preferred that the entire phosphor is
made of the crystal phase having the above-described chemical
composition of the formula [I].
[1-2. Object Color of the Phosphor of the Present Invention]
[0056] The causes for coloration of inorganic crystals are
generally classified into the following three types. (1) Coloration
due to a ligand field absorption band (crystal field coloration),
(2) coloration due to transition between molecular orbitals, and
(3) coloration due to transition within substances having energy
bands. Among them, the coloration (1) is due to the presence of an
element having an electronic state not to completely fill the inner
shell, such as a transition metal element or a rare earth element.
That is, such an incomplete inner shell has an unpaired electron,
and such an excited state imparts a color to a substance
corresponding to a visible spectrum. The emission center element to
be used in many phosphors is a transition metal element or a rare
earth element and thus is provided with the requirements for (1) in
consideration of a fact that no coloration is observed in the case
of a matrix crystal containing no emission center element.
[0057] From the foregoing, it is considered that as the object
color of the above phosphor, coloration unique to the phosphor is
observed, since at the same time as the light emitted from the
phosphor itself upon absorption of a visible light, light in a
region where the spectral reflectance is high, is reflected. The
object color is usually represented by means of the L*, a*, b*
color system (JIS Z8113). Here, L* does not exceed 100, since it is
usual to handle an object which does not emit light under
irradiation light, but in the case of the phosphor of the present
invention, it may exceeds 100, since the emitted light is
superimposed on the reflected light under excitation with the
irradiation light source, and its upper limit is usually
L*.ltoreq.110. Here, the measurement of the object color of the
phosphor of the present invention may be carried out, for example,
by means of a commercially available object color measuring
apparatus (such as CR-300 manufactured by MINOLTA).
[0058] As mentioned above, the phosphor of the present invention is
characterized in that when its object color is represented by the
L*a*b* color system, the values of a*, b* and
(a*.sup.2+b*.sup.2).sup.1/2 satisfy -20.ltoreq.a*.ltoreq.-2,
71.ltoreq.b* and 71.ltoreq.(a*.sup.2+b*.sup.2).sup.1/2,
respectively.
[0059] From the viewpoint of the color, a* is usually at least -20,
preferably at least -19, more preferably at least -18, further
preferably at least -17 and usually at most -2, preferably at most
-5, more preferably at most -8, further preferably at most -9, most
preferably at most -11. If a* is too small, the color tends to be
yellowish green, whereby it tends to be difficult to perform a
function as a yellow phosphor. If a* is too large, the color tends
to be reddish yellow, whereby it tends to be difficult to perform a
function as a good yellow phosphor.
[0060] By adjusting a* to be within the above range, it is possible
to obtain an object color of pure yellow. This means that in a blue
color which is in a complementary relation with the yellow color,
the blue light to be absorbed is a pure blue light. Therefore, when
the phosphor having a* within this range is combined with a
phosphor with another emission color such as a green phosphor or a
bluish green phosphor to form a device to emit the desired emission
color by using blue LED as the power source, it is possible to
present a light-emitting device with high luminous efficiency,
since it is thereby possible to suppress absorption of the emission
color of the second phosphor.
[0061] In such a combination of phosphors, the good characteristic
relating to this a* is an important characteristic which cannot be
accomplished by yellow emission properties by a yellow phosphor
alone e.g. by only a factor such as yellow light luminance. That
is, in a case where a yellow phosphor and another phosphor are
combined to form a light-emitting device, for example, among yellow
phosphors having the same luminance, one having a* within this
range will be excellent in the overall luminous efficiency.
[0062] Likewise, from the viewpoint of the color, b* is usually at
least 71, preferably at least 72, more preferably at least 73,
further preferably at least 74, and the upper limit is not
particularly limited, but is usually at most 105, preferably at
most 102, more preferably at most 100, further preferably at most
98. If b* is too small, the color tends to be blackish yellow,
whereby it tends to be difficult to perform a function as a good
yellow phosphor.
[0063] By adjusting b* to be within the above range, it is possible
to obtain an object color of yellow which is not blackish. A
substance having an object color of blackish yellow means that it
absorbs a visible light other than the wavelength of blue light,
such as in a green region or a red region, in addition to the blue
color which is in a complementary relation with a yellow color.
Therefore, when the phosphor having b* within this range and having
an object color of yellow which is not blackish, is combined with a
phosphor having another emission color such as a red phosphor or a
green phosphor to form a device to emit a desired emission color
such as a light bulb color emission or a warm white emission, by
using blue LED as a light source, it is possible to provide a
light-emitting device having a good luminous efficiency, since it
is thereby possible to substantially suppress absorption of green
or red emission of the second phosphor.
[0064] In such a combination of phosphors, the good characteristic
relating to this b* is an important characteristic which cannot be
accomplished by yellow emission properties by a yellow phosphor
alone, e.g. by only a factor such as yellow light luminance. That
is, in a case where a yellow phosphor is combined with another
phosphor to form a light-emitting device, for example, among yellow
phosphors having the same luminance, one having b* within this
range will be excellent in the overall luminous efficiency.
[0065] Further, from the viewpoint of chroma,
(a*.sup.2+b*.sup.2).sup.1/2 is usually at least 71, preferably at
least 72, more preferably at least 74, further preferably at least
76, and its upper limit is not particularly limited, but it is
usually at most 105, preferably at most 102, more preferably at
most 100, further preferably at most 98. If
(a*.sup.2+b*.sup.2).sup.1/2 is too small, the color tends to be a
dull color of yellow, and as (a*.sup.2+b*.sup.2).sup.1/2 becomes
high, the color becomes bright yellow such being preferred as a
yellow phosphor.
[0066] By adjusting (a*.sup.2+b*.sup.2).sup.1/2 to be within the
above range, it is possible to obtain an object color of
dullness-free yellow. A substance having an object color of yellow
with dullness means that it absorbs visible light other than a blue
color which is in a complementary relation with a yellow color, by
e.g. defects in the solid substance. Therefore, when the phosphor
having (a*.sup.2+b*.sup.2).sup.1/2 within this range and having an
object color of dullness-free yellow, is combined with a phosphor
having another emission color, such as a red phosphor or a green
phosphor to form a device to emit a desired emission color such as
a light bulb color emission or a warm white emission, by using blue
LED as a light source, it is possible to provide a light-emitting
device having a good luminous efficiency, since it is thereby
possible to suppress absorption of the green or red emission of the
second phosphor. In such a combination of phosphors, the good
characteristic relating to this (a*.sup.2+b*.sup.2).sup.1/2 is an
important characteristic which cannot be accomplished by the yellow
emission properties of a yellow phosphor alone, e.g. by only a
factor such as a yellow light luminance.
[1-3. Absorption Efficiency of the Phosphor of the Present
Invention]
[0067] The absorption efficiency of a phosphor means a ratio of the
number of photons absorbed by the phosphor to the number of photons
of excitation light. The absorption efficiency of the phosphor of
the present invention is not particularly limited, but should
better be high. Specifically, when the phosphor of the present
invention is excited with light having a wavelength of 455 nm, the
absorption efficiency is usually at least 88%, preferably at least
89%, more preferably at least 90%, further preferably at least 91%.
If the absorption efficiency of the phosphor is too low, the amount
of excitation light required to obtain the desired emission becomes
large, and the energy consumption becomes large, whereby the
luminous efficiency tends to be low. The method for measuring the
absorption efficiency is as shown in the section for "EXAMPLES"
given hereinafter.
[1-4. Other Properties of the Phosphor of the Present
Invention]
[1-4-1. Emission Color]
[0068] The phosphor of the present invention usually emits yellow
to orange light. That is, the phosphor of the present invention
usually becomes a yellow to orange phosphor. The chromaticity
coordinate of fluorescence of the phosphor of the present invention
usually becomes a coordinate with a region defined by (x,y)=(0.400,
0.420), (0.400, 0.590), (0.570, 0.590) and (0.570, 0.420), and
preferably becomes a coordinate within a region defined by
(x,y)=(0.420, 0.450), (0.420, 0.560), (0.560,0.560) and (0.560,
0.450). Therefore, in the chromaticity coordinate of fluorescence
of the phosphor of the present invention, the chromaticity
coordinate x is usually at least 0.400, preferably at least 0.420
and usually at most 0.570, preferably at most 0.560. On the other
hand, the chromaticity coordinate y is usually at least 0.420,
preferably at least 0.450 and usually at most 0.590, preferably at
most 0.560.
[0069] Especially when the luminance is important, the emission
color is preferably slightly greenish yellow, and in such a case,
the chromaticity coordinate x being from 0.41 to 0.43, and the
chromaticity coordinate y being from 0.55 to 0.56 will be the most
advantageous ranges.
[0070] Here, the chromaticity coordinates of fluorescence can be
calculated from the after-described emission spectrum. Further, the
values of the above chromaticity coordinates x and y represent
values of chromaticity coordinates in the CIE standard coordinate
system of an emission color when excited with light having a
wavelength of 455 nm. If a part of element R is substituted by
another rare earth element, e.g. if a part of La is substituted by
an element such as Y or Gd, it becomes possible to control the
chromaticity coordinate (x, y) values of the emission color, and it
becomes possible to present a width to the design of various
devices which will be described hereinafter.
[1-4-2. Emission Spectrum]
[0071] The spectrum (emission spectrum) of fluorescence emitted
from the phosphor of the present invention is not particularly
limited, but from the viewpoint of the application as a yellow to
orange phosphor, the emission peak wavelength of the emission
spectrum when excited with light having a wavelength of 455 nm is
usually at least 480 nm, preferably at least 500 nm, more
preferably at least 515 nm, further preferably at least 525 nm and
usually at most 640 nm, preferably at most 610 nm, more preferably
at most 600 nm. Further, in a case where the luminance is
particularly important, the emission peak wavelength is preferably
made to be from 530 nm to 535 nm.
[0072] Further, the phosphor of the present invention has a full
width at half maximum (hereinafter sometimes referred to as "FWHM")
of an emission peak when excited with light having a wavelength of
455 nm, being usually at least 100 nm, preferably at least 110 nm,
more preferably at least 115 nm. As the full width at half maximum
is wide like this, the color rendering properties of e.g. a
light-emitting device can be made good when the phosphor of the
present invention is combined with e.g. blue LED. Here, the upper
limit of the full width at half maximum of the emission peak is not
particularly limited, but it is usually at most 280 nm.
[0073] The measurement of the emission spectrum of the phosphor of
the present invention as well as the calculations of its luminous
region, the emission peak wavelength and the full width at half
value of the peak may, for example, be carried out at room
temperature (usually 25.degree. C.) by means of an apparatus such
as a fluorescence-measuring apparatus manufactured by JASCO
Corporation.
[1-4-3. Excitation Wavelength]
[0074] The wavelength of light to excite the phosphor of the
present invention (excitation wavelength) varies depending upon
e.g. the composition of the phosphor of the present invention.
However, usually, the excitation is preferably carried out by light
within a wavelength range of from a near ultraviolet region to a
blue region. A specific range of the excitation wavelength is
usually at least 300 nm, preferably at least 340 nm and usually at
most 500 nm, preferably at most 480 nm.
[1-4-4. Weight Median Diameter]
[0075] The phosphor of the present invention preferably has a
weight median diameter within a range of usually at least 0.1
.mu.m, preferably at least 0.5 .mu.m and usually at most 30 .mu.m,
preferably at most 20 .mu.m. If the weight median diameter is too
small, the luminance tends to decrease, and the phosphor particles
tend to agglomerate. On the other hand, if the weight median
diameter is too large, coating irregularities or clogging of e.g. a
dispenser to tend to result.
[1-5. Merits of the Phosphor of the Present Invention]
[0076] As described above, the phosphor of the present invention
substantially contains yellowish green to orange color components
and is capable of emitting fluorescence with a wide full width at
half maximum. That is, the phosphor of the present invention has a
sufficient emission intensity in a long wavelength region of from
yellowish green to orange colors, and in its emission spectrum, it
is capable of emitting light having an emission peak with an
extremely wide full width at half maximum. Accordingly, when the
phosphor of the present invention is applied to a white-emitting
device, such a white emitting device will be capable of emitting
white light having various color tones and high color rendering
properties, to meet with needs.
[0077] Further, the phosphor of the present invention is a phosphor
which is usually particularly efficiently excited by a
semiconductor light-emitting element for near ultraviolet emission
or blue emission thereby to emit a yellowish green to orange color
fluorescence. Further, the phosphor of the present invention is
usually less likely to be susceptible to deterioration of emission
efficiency due to a temperature rise, as compared with a YAG:Ce
phosphor which has been commonly used in white-emitting
devices.
[1-6. Uses of the Phosphor of the Present Invention]
[0078] There is no particularly limitation to uses of the phosphor
of the present invention. By utilizing the above merits, it may
suitably be used in fields of e.g. lighting, image display devices,
etc. Among them, it is suitable for the purpose of realizing
particularly high output lamps among common lighting LED,
especially white LED for light bulb color which has high luminance
and high color rendering properties and which has relatively low
color temperature. Further, as mentioned above, the phosphor of the
present invention is less susceptible to deterioration of luminous
efficiency due to a temperature rise, whereby by employing the
phosphor of the present invention for a light-emitting device, it
is possible to realize an excellent light-emitting device which has
high luminous efficiency and is less susceptible to deterioration
of luminous efficiency due to a temperature rise and which has high
luminance and a wide color reproduction range.
[0079] Especially, by utilizing the characteristic such that the
phosphor of the present invention can be excited with blue light or
near ultraviolet light, it can be suitably employed for various
light-emitting devices (e.g. "light-emitting devices of the present
invention" given hereinafter). In such a case, by adjusting the
types or proportions of the phosphors to be combined, it is
possible to produce light-emitting devices having various emission
colors. Particularly, the phosphor of the present invention is
usually a yellow to orange color phosphor, and accordingly, when it
is combined with an excitation light source which emits blue light,
it is possible to produce a white-emitting device. It is thereby
possible to obtain an emission spectrum similar to an emission
spectrum of so-called pseudo white [e.g. emission color of a
light-emitting device having blue LED and a phosphor emitting
yellow fluorescence (yellow phosphor) combined].
[0080] Further, by combining a red phosphor to the above
white-emitting device and further combining a green phosphor as the
case requires, it is possible to realize a light-emitting device
excellent in red color rendering properties or a light-emitting
device which emits light bulb color (warm white color). In a case
where an excitation light source which emits near ultraviolet
light, is used, by adjusting the emission wavelengths of a blue
phosphor, a red phosphor and/or a green phosphor in addition to the
phosphor of the present invention, it is possible to obtain a white
light source whereby a desired emission color can be obtained.
[0081] Further, the emission color of a light-emitting device is
not limited to white color. For example, in a case where a
light-emitting device is constituted by using the phosphor of the
present invention as a wavelength-conversion material, it is
possible to produce a light-emitting device which emits an optional
color, by combining other phosphors in addition to the phosphor of
the present invention and adjusting the types or proportions of the
phosphors. The light-emitting device thus obtained can be used as a
light-emitting portion for an image display device (particularly as
a backlight for liquid crystal or the like) or as a lighting
system.
[0082] Such other phosphors may, for example, be preferably
phosphors which exhibit emission of e.g. blue, bluish green, green,
yellowish green, red or deep red color. Particularly, by combining
the phosphor of the present invention, a green or red phosphor, and
as an excitation light source, a blue-emitting diode, it is
possible to constitute a white-emitting device, such being more
preferred. Further, it is possible to constitute a preferred
white-emitting device also by combining the phosphor of the present
invention with a near ultraviolet-emitting diode, a blue phosphor,
a red phosphor and a green phosphor. By adding a phosphor which
emits red to deep red color to such a white-emitting device, it is
possible to further improve the color rendering properties.
[2. Method for Producing the Phosphor of the Present Invention]
[0083] There is no particularly limitation to the method for
producing the phosphor of the present invention. Any optional
method may be employed so long as it is a method whereby a phosphor
having the above-described properties can be obtained. For example,
phosphor precursors are prepared as raw materials, and such
phosphor precursors may be mixed as the case requires, and the
phosphor can be produced via a step (firing step) of firing the
mixed phosphor precursors. Among such production methods, a method
is preferred wherein an alloy is used at least as a part of the raw
materials. More specifically, it is preferred to produce the
phosphor by a method which has a step of firing an alloy containing
at least elements of R, A and Si in the above formula [I]
(hereinafter sometimes referred to as "an alloy for production of a
phosphor" in the presence of a flux.
[0084] That is, the present invention provides a method for
producing a phosphor containing a crystal phase represented by the
following formula [I]
R.sub.3-x-y-z+w2M.sub.zA.sub.1.5x+y-w2Si.sub.6-w1-w2Al.sub.w1+w2O.sub.y+-
w1N.sub.11-y-w1 [I]
wherein R, M, A, x, y, z, w1 and w2 are as defined above, which
comprises nitriding an alloy for production of a phosphor,
containing at least elements of R, A and Si, wherein said alloy is
subjected to firing in the presence of a flux.
[0085] In the above production method, it is preferred to carry out
the firing under a temperature condition such that the rate of
temperature rise during the firing is at most 0.5.degree. C./min
within a temperature range corresponding to at least a part of the
low temperature side of an exothermic peak obtainable by TG-DTA
(thermogravimetry/differential thermal analysis) during the
nitriding reaction of the alloy for production of a phosphor.
Further, it is preferred to carry out the firing in a
hydrogen-containing nitrogen gas atmosphere. Further, it is
preferred that after the firing, the obtained fired product is
washed with an acidic aqueous solution. By using such methods in
combination as the case requires, it is possible to suitably
produce the phosphor of the present invention which has high
luminance and a specific object color.
[0086] Now, as an embodiment of the method for producing the
phosphor of the present invention, the method of employing such an
alloy for production of a phosphor will be described in further
detail.
[2-1. Alloy for Production of Phosphor]
[0087] As a purification method for metal simple substances to be
industrially widely used, sublimation purification, a floating zone
method or a distillation method is generally known. Among such
metal simple substances, there are many elements which are easy to
purify as compared with metal compounds. Accordingly, a method of
using required metal element simple substances as starting
materials for the production of a phosphor, alloying them and
producing a phosphor from the obtained alloy for production of a
phosphor, is superior to a method of using metal compounds as raw
materials, in that it is easy to obtain raw materials having a high
purity. Further, also from the viewpoint of uniform dispersion of
activation elements in the crystal lattice, it is preferred that
the raw materials for constituting elements are metal simple
substances, whereby they may be melted and alloyed, so that the
activation elements can easily and uniformly be dispersed.
[0088] From the above viewpoint, by using, as a raw material, an
alloy for production of a phosphor, containing at least a part of
metal elements constituting the desired phosphor, preferably an
alloy for production of a phosphor containing all metal elements
constituting the desired phosphor, and producing a phosphor by
nitriding the alloy, it is possible to industrially produce a
phosphor having a high performance.
[2-1-1. Composition of Alloy]
[0089] The alloy for production of a phosphor may be an alloy of
any composition so long as it is an alloy containing at least
elements of R, A and Si in the above formula [I]. Here, preferred
types of such elements constituting the alloy are as mentioned
above.
[0090] Preferred as the alloy for production of a phosphor is one
having a composition represented by the following formula [II]:
R.sub.aM.sub.bA.sub.cSi.sub.6Al.sub.e [II]
wherein R is at least one rare earth element selected from the
group consisting of La, Gd, Lu, Y and Sc, M is at least one metal
element selected from the group consisting of Ce, Eu, Mn, Yb, Pr
and Tb, A is at least one bivalent metal element selected from the
group consisting of Ba, Sr, Ca, Mg and Zn, and a, b, c and e
represent the numerical values within the following ranges,
respectively: 1.ltoreq.a.ltoreq.4, 0.ltoreq.b.ltoreq.1,
0<c.ltoreq.4 and 0.ltoreq.e.ltoreq.2.
[0091] Here, preferred types of elements R, M and A in the formula
[II] are the same as in the above formula [I]. With a view to
suppressing cation defects, the value of a+b+c is more preferably
at least the value of 3+e/2. The alloy raw material of the formula
[II] is most preferably a single phase, but may not necessarily be
a single phase, i.e. it is possible to use one wherein to a main
phase being a single phase, another phase is intimately mixed, for
example, in a .mu.m order or a 100 nm order. For example, in the
case of Ca.sub.0.45La.sub.2.6Ce.sub.0.1Si.sub.6, one wherein to a
Ca.sub.0.3La.sub.2.6Ce.sub.0.1Si.sub.6 single phase, Ca.sub.0.15 is
intimately mixed may be mentioned as an example.
[2-1-2. Particle Diameter of Alloy]
[0092] The average particle diameter (weight median diameter
D.sub.50) of an alloy for production of a phosphor is usually at
least 1 .mu.m, preferably at least 2 .mu.m, more preferably at
least 3 .mu.m and usually at most 8 .mu.m, preferably at most 7.5
.mu.m, more preferably at most 7 .mu.m. Even if the alloy contains
a non-uniform portion, homogenization is carried out by this
pulverization step macroscopically, but microscopically, the
pulverized particles having different compositions cannot be
regarded as a preferred state. Therefore, it is desired that the
entire alloy is homogeneous.
[2-1-3. Contents of Carbon and Oxygen in the Alloy]
[0093] As impurities contained in the alloy, various elements are
possible. It is preferred to use, as the raw material for the
production of a phosphor, an alloy wherein the carbon content is
less than 1 wt %. The upper limit is usually at most 1 wt %,
preferably at most 0.3%, most preferably at most 0.1%, further
preferably at most 0.01%. The lower limit is not particularly
limited. However, for the stability of the quality for the
production, a certain amount of at most 0.01% may be added.
[0094] In a case where in the step of converting the alloy
containing the above-mentioned amount of carbon to a phosphor,
firing is carried out in an atmosphere gas of hydrogen-containing
nitrogen, the amount of carbon in the phosphor will be
substantially reduced. It is considered that the carbon in the
alloy is reacted with hydrogen to form a hydrocarbon.
[0095] Further, oxygen in the alloy is likely to be included in
various steps among steps for producing the alloy. It is preferred
to use, as the raw material for production of a phosphor, an alloy
wherein the oxygen content is less than 2 wt %. From the viewpoint
of the luminance, the upper limit is usually less than 2 wt %,
preferably at most 0.6%, more preferably at most 0.1%. If it is too
much, the oxygen contamination amount during the firing tends to be
large, whereby it tends to be difficult to obtain the phosphor of
the present invention having high luminance. The lower limit is not
particularly limited.
[0096] In a case where hydrogen-containing nitrogen is used as the
atmosphere gas in the step of converting the alloy containing the
above amount of oxygen to a phosphor, the oxygen content in the
phosphor may be maintained or reduced. Usually, via a firing step,
the amount of oxygen in the phosphor is likely to increase over the
oxygen content in the starting material in many cases, but it is
considered that by conversion to CO and/or H.sub.2O, the amount of
oxygen in the phosphor is maintained or reduced. Here, the contents
of carbon and oxygen in the alloy can be measured by the methods
shown in the section of "EXAMPLES" given hereinafter.
[2-2. Preparation of Alloy for Production of Phosphor]
[0097] The alloy for production of a phosphor having the
above-described composition and physical properties can be prepared
as follows. Firstly, an alloy for production of a phosphor to be a
raw material for a phosphor is prepared. At the time of preparing
the alloy for production of a phosphor, usually, starting materials
such as metal simple substances, metal alloys, etc. (hereinafter
sometimes referred to as "raw material metals") are melted to
obtain an alloy for production of a phosphor. In such a case, there
is no limitation to the melting method, and a known melting method
such as an arc melting method or a high frequency induction heating
method (a high frequency melting method) may, for example, be
used.
[2-2-1. Types of Raw Material Metals]
[0098] As the raw material metals, metals, alloys of such metals,
etc. may be used. Further, the raw material metals corresponding to
elements which the phosphor of the present invention contains, may
be in an optional combination and ratio, taking into consideration
a loss such as vaporization of a part of components in the
after-mentioned melting step. However, among the raw material
metals, as the raw material metals of metal element M being an
activation element (such as the raw material metals corresponding
to Eu, Ce, etc.), it is preferred to use Eu metal or Ce metal,
since such raw materials are readily available.
[0099] The raw materials for the alloy for production of the
phosphor of the present invention, other than the formula [II],
include, for example, LaSi.sub.2, Ce.sub.xLa.sub.1-xSi.sub.2
(0<x<1), LaSi, La.sub.3Si.sub.2, La.sub.5Si.sub.3,
Ca.sub.24Si.sub.60, Ca.sub.28Si.sub.60, CaSi.sub.2,
Ca.sub.31Si.sub.60, Ca.sub.14Si.sub.19, Ca.sub.3Si.sub.4, CaSi,
Ca.sub.5Si.sub.3, Ca.sub.2Si, Ca.sub.xLa.sub.3-xSi.sub.6
(0<x<3), Ce.sub.yCa.sub.xLa.sub.3-x-ySi.sub.6 (0<x<3,
0<y<3), Ca.sub.7Si, Ca.sub.2Si, Ca.sub.5Si.sub.3, CaSi,
Ca.sub.2Si.sub.2, Ca.sub.14Si.sub.19, Ca.sub.3Si.sub.4, SrSi,
SrSi.sub.2, Sr.sub.4Si.sub.7, Sr.sub.5Si.sub.3, Sr.sub.7Si, etc.
Further, an alloy containing Si, aluminum and an alkaline earth
metal may, for example, be one having alloy phases of e.g.
Ca(Si.sub.1-xAl.sub.x).sub.2, Sr(Si.sub.1-xAl.sub.x).sub.2,
Ba(Si.sub.1-xAl.sub.x).sub.2 and
Ca.sub.1-xSr.sub.x(Si.sub.1-yAl.sub.y).sub.2 suitably combined.
Particularly, LaSi, La.sub.3Si.sub.2, La.sub.5Si.sub.3 and an alloy
having a part of its La position substituted by Ce, are preferred.
Among them, LaSi is preferred, since the ratio of La is low,
whereby the safety in handling is high. In such a case, in order to
obtain La.sub.3Si.sub.6N.sub.11 crystal, Si.sub.3N.sub.4 tends to
be deficient, and it is necessary to heat the raw material having a
silicon source added, to prepare the phosphor. As such a silicon
source, Si.sub.3N.sub.4 is preferred.
[2-2-2. Purity of Raw Material Metals]
[0100] The purity of metals to be used as raw material metals for
the alloy for production of a phosphor should better be high.
Specifically, from the viewpoint of the emission characteristics of
the phosphor to be prepared, as a raw material metal corresponding
to activation element M, it is preferred to use a metal purified to
such an extent that impurities are usually at most 0.1 mol %,
preferably at most 0.01 mol %. Further, also a metal to be used as
a raw material metal for an element other than activation element M
preferably has an impurity concentration of at most 0.1 mol %, more
preferably at most 0.01 mol %, for the same reason as in the case
of activation element M. For example, when at least one member
selected from the group consisting of Fe, Ni and Co is contained as
an impurity, the content of each impurity element is usually at
most 500 ppm, preferably at most 100 ppm.
[2-2-3. Shape of Raw Material Metals]
[0101] There is no particularly limitation to the shape of raw
material metals, but usually, granular or massive ones having a
diameter of from a few mm to a few tens mm are used. Here, ones
having a diameter of at least 10 mm are referred to as massive, and
ones having a diameter less than 10 mm are referred to as
granular.
[0102] Further, raw material metals corresponding to alkaline earth
metal elements are not concerned about their shapes such as
granular or massive shapes, and a proper shape is preferably
selected depending upon the chemical nature of the particular raw
material metals. For example, Ca is stable and useful in the
atmospheric air in either granular or massive form, while Sr is
chemically more active, and therefore it is preferred to use a
massive raw material.
[0103] Further, a metal element to be lost by its evaporation
during the melting or its reaction with a crucible material, may be
preliminarily excessively weighed and used, as the case
requires.
[2-2-4. Melting of Raw Material Metals]
[0104] After weighing raw material metals, such raw material metals
are melted and alloyed to produce an alloy for production of a
phosphor (melting step). At the time of melting the raw material
metals, there is the following problem, particularly in the case of
producing an alloy for production of a phosphor containing Si, rare
earth element and an alkaline earth element.
[0105] The melting point of Si is 1,410.degree. C., which is the
same level as the boiling point of an alkaline earth metal (e.g.
the boiling point of Ca is 1,494.degree. C., the boiling point of
Sr is 1,350.degree. C. and the boiling-point of Ba is 1,537.degree.
C.). Therefore, there has been a problem such that the alkaline
earth metal-undergoes evaporation during the melting, whereby an
alloy having the desired composition cannot be obtained.
[0106] Therefore, in the present invention, the composition of the
alloy to be formed is controlled by utilizing the nature of an
eutectic point composition of Si and rare earth element alloy, e.g.
in the case of a Si--La type alloy, the eutectic point temperature
of LaSi.sub.2 is 1,205.degree. C. which is lower than the melting
point of Si simple substance. That is, it has been found possible
to obtain an alloy having a prescribed composition by firstly
arranging so that an alloy with a composition having a melting
point close to the eutectic point will be formed first, for
example, by arranging the charging so that (La, Ca)Si.sub.2 will be
formed first and then, the rest of metals will be melted therein,
and thus, the above problem has been solved. Further, there will be
such an effect that the purity of the obtainable alloy will be
improved, and the properties of a phosphor prepared by using it as
the raw material will be remarkably improved.
[0107] The obtainable alloy for production of a phosphor is one
containing at least elements of R, A and Si among metal elements
constituting the phosphor of the present invention, and is
preferably one having a composition represented by the above
formula [II]. Further, even in a case where one alloy for
production of a phosphor does not contain all of the metal elements
to constitute the phosphor of the present invention, it is possible
to produce the phosphor of the present invention by using two or
more alloys for production of phosphors and/or other raw materials
(such as metals) in combination in the subsequent firing step.
[0108] There is no particularly limitation to the method for
melting raw material metals, and an optional method may be adopted.
For example, it is possible to employ a resistance heating method,
an electron beam method, an arc melting method, a high frequency
induction heating method (high frequency melting method) or the
like. Further, two or more of such methods may be used in an
optional combination for the melting.
[0109] Further, the material for a crucible useful for the melting
may, for example, be alumina, calcia, graphite, molybdenum, boron
nitride or iridium. Further, to prevent inclusion of the crucible
material, it is possible to employ a high frequency melting method
employing a water-cooled copper crucible (so-called scull melting
method or cold crucible melting method). This method is very
preferable as a method for producing an alloy for the present
phosphor, of which the melting point exceeds 1,500.degree. C.
[0110] However, in the case of producing an alloy for production of
a phosphor containing metal elements which cannot be melted
simultaneously, such as Si and alkaline earth metal elements, the
alloy for production of a phosphor may be produced by producing a
matrix alloy and then mixing other metal raw materials. For a
detailed method in such a case, WO2006/106948 may be referred
to.
[0111] In the case of melting any raw material metal, with respect
to the specific temperature condition and melting time at the time
of melting the raw material metal, a suitable temperature and time
may be set depending upon the raw material metal to be used.
Further, the atmosphere during the melting of the raw material
metal is optional so long as an alloy for the production of a
phosphor is thereby obtainable, but an inert gas atmosphere is
preferred, and an argon atmosphere is particularly preferred. Here,
one of inert gases may be used alone, or two or more of them may be
used in an optional combination and ratio. Further, the pressure
during the melting of the raw material metals is optional so long
as an alloy for production of a phosphor can thereby be obtainable,
but it is preferably at least 1.times.10.sup.3 Pa and preferably at
most 1.times.10.sup.5 Pa. Further, also from the viewpoint of
safety, it is preferred to carry out the melting under atmospheric
pressure or lower.
[2-2-5. Casting of Melt]
[0112] By the above-described melting of raw material metals, an
alloy for production of a phosphor is obtained. This alloy for
production of a phosphor is obtained usually as an alloy melt,
however, there are many technical problems to directly produce a
phosphor from such an alloy melt. Therefore, it is preferred to
obtain a solidified product (hereinafter sometimes referred to as
an "alloy lump") via a casting step wherein the alloy melt is cast
in a mold.
[0113] However, there may be a case where in this casting step,
segregation results by a cooling speed of molten metals, whereby
the alloy for production of a phosphor having a uniform composition
in a molten state is likely to have a deviation in the distribution
of the composition. Accordingly, the cooing speed should better be
fast. Further, the mold is preferably made of a material having
good thermal conductivity such as copper, and is preferably in a
shape to readily release the heat. Further, as the case requires,
it is also preferred to cool the mold by such a means as cooling
with water.
[0114] As such an idea, it is, for example, preferred that by using
a mold having a large bottom surface to the thickness, the melt is
solidified as quickly as possible after being poured into the
mold.
[0115] Further, the degree of such deviation varies depending upon
the composition of the alloy for production of a phosphor, and it
is preferred that by sampling samples from several portions of the
obtained solidified product and carrying out an analysis of the
composition by means of a necessary analyzing means such as an ICP
emission spectroscopic analysis, the cooling speed required to
prevent the segregation is determined.
[0116] Further, the atmosphere during the casting is preferably an
inert gas atmosphere, particularly preferably an argon atmosphere.
At that time, one of such inert gases may be used alone, or two or
more of them may be used in an optional combination and ratio.
[2-2-6. Pulverization of Alloy Lumps]
[0117] The alloy for production of a phosphor may be in the form of
lumps, or powder. However, in the form of lumps, the reaction to
form a phosphor tends to hardly proceed, and therefore, it is
preferred to pulverize them to a predetermined particle diameter,
prior to the firing. Therefore, the alloy lumps obtained by the
casting are pulverized (pulverization step) to obtain a powder of
an alloy for production of a phosphor (hereinafter sometimes
referred to as an "alloy powder") having the desired particle
diameter and particle size distribution.
[0118] Here, from the viewpoint of the production of a phosphor
having high luminance and safe raw materials, if the particle
diameter of the alloy is too large, nitriding tends to hardly take
place, whereby the luminance of the obtainable phosphor tends to be
low. Further, if it is too small, in the pulverization step of the
powder, a danger of ignition of the powder increases due to leakage
of the powder into the atmospheric air or leakage of the
atmospheric air to the powder, and at the same time, deterioration
of the luminance is likely to occur due to an increase of the
oxygen contamination amount.
[0119] The pulverization method is not particularly limited, and
for example, the pulverization can be carried out by a dry method
or a wet method using an organic solvent such as ethylene glycol,
hexane or acetone.
[0120] Now, the method will be described in detail with reference
to the dry method. This pulverization step may be carried out
dividedly in a plurality of steps such as a roughly pulverizing
step, an intermediately pulverizing step and a finely pulverizing
step, as the case requires. In such a case, in all pulverization
steps, the same apparatus may be used for pulverization, but the
apparatus may be changed depending upon the particular step.
[0121] Here, the roughly pulverizing step is a step of
pulverization so that about 90 wt % of the alloy powder will have a
particle diameter of at most 1 cm, and for example, a pulverization
apparatus such as a jaw crusher, a gyratory crusher, a crushing
roll or an impact crusher may be used. The intermediately crushing
step is a step of pulverization so that about 90 wt % of the alloy
powder will have a particle diameter of at most 1 mm, and for
example, a pulverization apparatus such as a corn crusher, a
crushing roll, a hammer mill or a disk mill may, for example, be
used. The finely pulverizing step is a step of pulverization so
that the alloy powder will have the after-mentioned weight median
diameter, and for example, a pulverizing apparatus such as a ball
mill, a tube mill, a rod mill, a roller mill, a stamp mill, an edge
runner, a vibration mill or a jet mill may be used.
[0122] With a view to preventing inclusion of impurities, in the
final pulverization step, it is preferred to use a jet mill. To use
a jet mill, the alloy lumps are preferably preliminarily pulverized
to a particle diameter of at most about 2 mm. In a jet mill,
pulverization of particles is carried out by utilizing the
expansion energy of a fluid jetted from the nozzle initial pressure
to the atmospheric pressure, whereby it is possible to control the
particle diameter by the pulverization pressure and to prevent
inclusion of impurities. The pulverization pressure varies
depending upon the apparatus, but it is usually at least 0.01 MPa,
preferably at least 0.05 MPa, more preferably at least 0.1 MPa and
usually at most 2 MPa, preferably at most 0.4 MPa, more preferably
at most 0.3 MPa, by gauge pressure. If the gauge pressure is too
low, the particle diameter of the obtainable particles is likely to
be too large, and if it is too high, the particle diameter of the
obtainable particles is likely to be small.
[0123] In any case, it is preferred to properly select the relation
between the material of the pulverizer and the object to be
pulverized so as to avoid inclusion of impurities such as iron
during the pulverization step. For example, the portion in contact
with the powder preferably has a ceramic lining applied, and among
ceramics, alumina, silicon nitride, tungsten carbide or zirconia
may, for example, be preferred. Here, they may be used alone, or
two or more of them may be used in an optional combination and
ratio.
[0124] In order to prevent oxidation of the alloy powder, it is
preferred to carry out the pulverization step in an inert gas
atmosphere. The type of the inert gas is not particularly limited,
but usually, it is possible to use a single atmosphere of one gas
among nitrogen, argon, helium, etc. or a mixed atmosphere of two or
more such gases. Among them, nitrogen is particularly preferred
from the viewpoint of the economical efficiency.
[0125] The oxygen concentration in the atmosphere is not
particularly limited so long as oxidation of the alloy powder can
be prevented, but it is usually at most 10 vol %, particularly
preferably at most 5 vol %. Further, the lower limit of the oxygen
concentration is usually about 10 ppm. It is considered that by
adjusting the oxygen concentration to be within the specified
range, an oxidized coating film will be formed on the surface of
the alloy during the pulverization, whereby the powder will be
stabilized. In a case where the pulverization step is carried out
in an atmosphere wherein the oxygen concentration is higher than 5
vol %, it is possible that the powder dust will explode during the
pulverization, and therefore, it is preferred to provide an
equipment not to let such powder dust be formed.
[0126] Further, cooling may be applied, as the case requires, to
prevent a temperature rise of the alloy powder during the
pulverization step.
[2-2-7. Classification of Alloy Powder]
[0127] The alloy powder obtained as described above is preferably
adjusted to have the desired weight median diameter D.sub.50 and
particle size distribution (classification step) by means of e.g. a
sieving apparatus using a mesh such as a vibration screen or a
shifter; an inertial classification apparatus such as an air
separator; or a centrifugal separator such as a cyclone, and then
subjected to the subsequent steps.
[0128] Here, in the adjustment of the particle size distribution,
it is preferred that coarse particles are classified and recycled
to the pulverizer, and it is more preferred that the classification
and/or the recycling is continuous.
[0129] The classification step is also preferably carried out in an
inert gas atmosphere. The type of the inert gas is not particularly
limited, but usually, a single atmosphere of one gas among
nitrogen, argon, helium, etc. or a mixed atmosphere of two or more
such gases, is used and nitrogen is particularly preferred from the
viewpoint of the economical efficiency. Further, the oxygen
concentration in the inert gas atmosphere is preferably at most 10
vol %, particularly preferably at most 5 vol %.
[2-2-8. Preparation of the Alloy by Atomizing Method or the
Like]
[0130] The alloy for production of a phosphor may be produced via
the following steps (a) to (c), other than the production by the
above-described method. It is thereby possible to obtain a powder
of an alloy for production of a phosphor having an angle of repose
of at most 45.degree.. (a) Two or more among raw material metals
corresponding to the metals constituting the phosphor are melted to
prepare an alloy melt containing such elements (melting step). (b)
The alloy melt is atomized in an inert gas (atomizing step). (c)
The atomized alloy melt is solidified to obtain an alloy powder
(solidification step).
[0131] That is, this method is one wherein the alloy melt is
atomized in a gas, followed by solidification to obtain a powder.
The above atomizing step (b) and the solidification step (c) are
preferably carried out, for example, by a method of spraying the
alloy melt, a method of quenching by means of a roll or a gas
stream to finely form the alloy melt into a ribbon, or an atomizing
method to obtain a powder. Among them, it is preferred to employ an
atomizing method. Specifically, a known method disclosed in
WO2007/135975 may be employed by suitable modification as the case
requires.
[2-3. Firing Step]
[0132] The obtained alloy for production of a phosphor is fired in
the presence of flux and nitrided to obtain a phosphor of the
present invention. Here, the firing is preferably carried out in a
hydrogen-containing nitrogen gas atmosphere, as described
hereinafter.
[2-3-1. Mixing of Raw Materials]
[0133] In a case where the composition of metal elements contained
in the alloy for production of a phosphor agrees to the composition
of metal elements contained in the crystal phase represented by the
formula [I], only the alloy for production of a phosphor may be
fired. On the other hand, in a case where they do not agree, the
alloy for production of a phosphor is mixed with an alloy for
production of a phosphor, metal simple substances, metal compounds,
etc. having another composition to adjust so that the composition
of metal elements contained in the raw materials will agree to the
composition of metal elements contained in the crystal phase
represented by the formula [I], and then the firing is carried
out.
[0134] Here, even in a case where the composition of metal elements
contained in the alloy for production of a phosphor agrees to the
composition of metal elements contained in the crystal phase
represented by the formula [I], if a nitride or oxynitride (which
may be a nitride or oxynitride containing an activation element of
the phosphor of the present invention itself) is mixed to the alloy
for production of a phosphor, it becomes possible to suppress the
heat generation rate per unit volume during the nitriding thereby
to let the nitriding reaction proceed smoothly, as disclosed in
WO2007/135975, whereby it becomes possible to obtain a phosphor
having high properties at a high productivity. For the production
of the phosphor of the present invention, the nitriding treatment
may be carried out in the presence of a suitable nitride or
oxynitride with reference to WO2007/135975 with suitable
modifications as the case requires.
[0135] At that time, there is no particular limitation to metal
compounds which may be used as mixed to the alloy for production of
a phosphor, and for example, a nitride, an oxide, a hydroxide, a
carbonate, a nitrate, a sulfate, an oxalate, a carboxylate, a
halide, etc. may be mentioned. Specific types may suitably be
selected among these metal compounds in consideration of e.g. low
generation of NO.sub.x or SO.sub.x during the firing or the
reactivity to the desired product. However, from such a viewpoint
that the phosphor of the present invention is a nitrogen-containing
phosphor, it is preferred to use a nitride and/or oxynitride. Among
them, it is particularly preferred to employ a nitride, since it
also plays a role as a nitrogen source.
[0136] Specific examples of the nitride and oxynitride include
nitrides of elements constituting the phosphor, such as AlN,
Si.sub.3N.sub.4, Ca.sub.3N.sub.2, Sr.sub.3N.sub.2, EuN, etc., and
composite nitrides of elements constituting the phosphor, such as
CaAlSiN.sub.3, (Sr,Ca)AlSiN.sub.3, (Sr,Ca).sub.2Si.sub.5N.sub.8,
CaSiN.sub.2, SrSiN.sub.2, BaSi.sub.4N.sub.7, etc. Further, the
above nitrides may contain a very small amount of oxygen. In the
nitrides, the ratio (molar ratio) of oxygen/(oxygen+nitrogen) is
optional so long as the phosphor of the present invention is
thereby obtainable, but it is usually at most 5%, preferably at
most 1%, more preferably at most 0.5%, further preferably at most
0.3%, particularly preferably at most 0.2%. If the ratio of oxygen
in a nitride is too much, the luminance is likely to be low.
[0137] The weight median diameter D.sub.50 of a metal compound is
not particularly limited so long as there is no trouble in mixing
with other raw materials. However, it is preferably readily mixed
with other raw materials, and for example, it is preferably at the
same level as the alloy powder. The specific value for the weight
median diameter D.sub.50 of a metal compound is optional so long as
the phosphor can be obtained, but it is preferably at most 200
.mu.m, more preferably at most 100 .mu.m, particularly preferably
at most 80 .mu.m, further preferably at most 60 .mu.m and
preferably at least 0.1 .mu.m, more preferably at least 0.5 .mu.m.
Further, each of the above-mentioned alloy for production of a
phosphor, metal simple substance, metal compound, etc. may be used
alone, or two or more of them may be used in an optional
combination and ratio.
[0138] It is preferred that an alloy for production of a phosphor,
containing all of metal elements to constitute a phosphor, is
prepared, and a phosphor is produced by firing such an alloy,
whereby it is possible to simply produce a good phosphor in a small
number of steps. Further, in a conventional production method
wherein an alloy is not used, there has been a case where a
phosphor having a desired element composition ratio cannot be
obtained as the compositional ratio of the metal elements contained
in the raw materials has changed by e.g. the firing. Whereas, by
using an alloy for production of a phosphor, it is possible to
simply obtain a phosphor having the desired compositional ratio
simply by charging metal elements along the stoichiometry of the
desired phosphor.
[2-3-2. Flux]
[0139] In the firing step, it is preferred that a flux is permitted
to coexist in the reaction system with a view to letting good
crystals grow.
[0140] The type of the flux is not particularly limited, and it
may, for example, be ammonium halide such as NH.sub.4Cl or
NH.sub.4F.HF; an alkali metal carbonate such as NaCO.sub.3 or
LiCO.sub.3; an alkali metal halide such as LiCl, NaCl, KCl, CsCl,
LiF, NaF, KF or CsF; an alkaline earth metal halide such as
CaCl.sub.2, BaCl.sub.2, SrCl.sub.2, CaF.sub.2, BaF.sub.2,
SrF.sub.2, MgCl.sub.2 or MgF.sub.2; an alkaline earth metal oxide
such as BaO; boron oxide, boric acid or an alkali metal or alkaline
earth metal borate compound such as B.sub.2O.sub.3, H.sub.3BO.sub.3
or Na.sub.2B.sub.4O.sub.7; a phosphate compound such as
Li.sub.3PO.sub.4 or NH.sub.4H.sub.2PO.sub.4; an aluminum halide
such as AlF.sub.3; a zinc compound such as a zinc halide such as
ZnCl.sub.2 or ZnF.sub.2, or zinc oxide, a compound of a Group 15
element of the Periodic Table, such as Bi.sub.2O.sub.3 or a nitride
of an alkali metal, alkaline earth metal or Group 13 element, such
as Li.sub.3N, Ca.sub.3N.sub.2, Sr.sub.3N.sub.2, Ba.sub.3N.sub.2 or
BN.
[0141] Further, the flux may, for example, be a halide of a rare
earth element, such as LaF.sub.3, LaCl.sub.3, GdF.sub.3,
GdCl.sub.3, LuF.sub.3, LuCl.sub.3, YF.sub.3, YCl.sub.3, ScF.sub.3
or ScCl.sub.3, or an oxide of a rare earth element, such as
La.sub.2O.sub.3, Gd.sub.2O.sub.3, Lu.sub.2O.sub.3, Y.sub.2O.sub.3
or Sc.sub.2O.sub.3.
[0142] As the above flux, a halide is preferred, and specifically,
a halide such as an alkali metal halide, an alkaline earth metal
halide, a halide of Zn or a halide of a rare earth element, is
preferred. Further, among halides, a fluoride or a chloride is
preferred, and further preferred is a fluoride. Specifically, an
alkali metal fluoride, an alkaline earth metal fluoride, ZnF.sub.2
or a fluoride of a rare earth element, is preferred, and
particularly preferred is a rare earth metal fluoride or an
alkaline earth metal fluoride.
[0143] Here, an anhydride should better be used for one having a
deliquescent nature among the above fluxes. Further, one of the
fluxes may be used alone, or two or more of them may be used in an
optional combination and ratio.
[0144] As a further preferred flux, MgF.sub.2 may be mentioned, but
other than that, CeF.sub.3, LaF.sub.3, YF.sub.3 or GdF.sub.3 may
also be suitably used. Among them, YF.sub.3, GdF.sub.3, etc. have
an effect to change the chromaticity coordinate (x,y) of the
emission color. In a case where CeF.sub.3 is used, Ce being a light
emission center may not be contained in the raw material (an alloy
or a mixture of an alloy with a nitride) constituting the matrix
crystal, such being desirable. When Ce is incorporated in the
alloy, it may be localized by e.g. segregation, since its amount is
small. Accordingly, from the viewpoint of the stability for the
production, it is particularly preferred to use CeF.sub.3.
[0145] The amount of the flux to be used varies depending on the
type of the raw material or the material for the flux and is
optional, but it is usually within a range of at least 0.01 wt %,
preferably at least 0.1 wt %, more preferably at least 0.3 wt % and
usually at most 20 wt %, preferably at most 10 wt %, based on the
entire raw material. If the amount of the flux is too small, the
effect of the flux may not be obtained, and if the amount of the
flux is too much, the effect of the flux is likely to be saturated,
or it is likely to be included in the matrix crystal to change the
emission color or to bring about deterioration of the luminance, or
to bring about deterioration of the firing furnace.
[2-3-3. Heating Conditions]
[0146] The alloy powder thus obtained and other compounds added, as
the case requires, are usually filled in a crucible or a container
such as a tray, which is then set in a heating furnace capable of
controlling the atmosphere. At that time, as the material for the
firing container to be used here, boron nitride, silicon nitride,
carbon, aluminum nitride, molybdenum or tungsten may, for example,
be mentioned, since the reactivity with the metal compounds is low
as the material for the container. Among them, molybdenum or boron
nitride is preferred, since it is excellent in corrosion
resistance. Further, one of such materials may be used alone, or
two or more of them may be used in an optional combination and
ratio.
[0147] The shape of the firing container to be used here is
optional. For example, the bottom surface of the firing container
may be no angular shape such as circular or oval, or a polygonal
shape such as triangular or square, and the height of the firing
container is also optional so long as acceptable in the heating
furnace and may be low or high. It is preferred to select a shape
which presents a good heat releasing property.
[0148] And, by heating the alloy powder, the phosphor of the
present invention can be obtained. Here, the alloy powder is
preferably fired in a state where it is held at a volume filling
rate of at most 40%. Here, the volume filling rate can be obtained
by (bulk density of the mixed powder)/(theoretical density of the
mixed powder).times.100[%].
[0149] The firing container filled with such a raw material for a
phosphor is set in a firing apparatus (hereinafter sometimes
referred to as "a heating furnace"). The firing apparatus to be
used here is optional so long as the effects of the present
invention can be obtained, but an apparatus capable of controlling
the atmosphere in the apparatus is preferred, and an apparatus
capable of controlling also the pressure is further preferred. For
example, a hot isostatic press apparatus (HIP) or a
resistance-heating type vacuum pressure atmosphere thermal
treatment furnace is preferred. Further, it is preferred that
before initiation of the heating, a gas containing nitrogen is
permitted to flow in the firing apparatus to sufficiently replace
the interior of the system with this nitrogen-containing gas. As
the case requires, after evacuating the interior of the system, the
nitrogen-containing gas may be introduced.
[0150] As the nitrogen-containing gas to be used for the nitriding
treatment, a gas containing nitrogen element such as nitrogen,
ammonia or a mixed gas of nitrogen and hydrogen, may, for example,
be mentioned. Further, one of such nitrogen-containing gases may be
used alone, or two or more of them may be used in an optional
combination and ratio. Among them, a nitrogen gas containing
hydrogen (hydrogen-containing nitrogen gas) is preferred as the
nitrogen-containing gas. Here, the mixing proportion of hydrogen in
the hydrogen-containing nitrogen gas is preferably at most 4 vol %,
since this is outside the explosion limit and thus is safe.
[0151] The first effective reason as to why it was possible to
realize a nitride yellow phosphor having high luminance and a
specific object color by employing an alloy as the raw material,
and the hydrogen gas-containing nitrogen gas, is considered to be
as follows. That is, in order for the metal to be nitrided,
nitrogen molecules are required to be dissociated, and it is
considered that hydrogen radicals are formed on the alloy surface,
and they assist the dissociation of the nitrogen molecules to
accelerate nitriding of the alloy by dissociated nitrogen. It is
known that when nitrogen atoms in a gas phase are dissociated and
adsorbed on the surface of a metal such as a transition metal, H
radicals assist such dissociation and adsorption, whereby NHx
species having two atomic molecules of nitrogen dissociated, will
be readily formed on the surface.
[0152] Further, as the second reason as to why it was possible to
realize the high luminance and the specific object color, it is
considered that hydrogen in the gas phase is reacted with a small
amount of carbon during the firing to suppress the amount of carbon
in the phosphor thereby to suppress deterioration of the luminance
due to the coexisting carbon. After the firing under
N.sub.2--H.sub.2, it was confirmed that the amount of carbon in the
solid was reduced to a half. Thus, it is considered that in a case
where the alloy is used as the raw material, coexistence of
hydrogen atoms in addition to nitrogen atoms presents good effects
to remove carbon and to assist good nitriding with less nitrogen
deficiency. In that sense, it is also preferred to use ammonia gas
containing both nitrogen atoms and hydrogen atoms, so long as gas
tightness of the firing furnace is ensured.
[0153] The oxygen concentration in the system is influential over
the oxygen content of the phosphor to be produced, and if the
content is too high, high luminance tends to be hardly obtainable.
Accordingly, the oxygen concentration in the atmosphere for
nitriding treatment should better be low, and it is usually at most
0.1 vol %, preferably at most 100 ppm, more preferably at most 10
ppm, further preferably at most 5 ppm. Further, as the case
requires, the oxygen concentration may be lowered by introducing an
oxygen getter such as carbon or molybdenum into the heating portion
in the system. Here, one of oxygen getters may be used alone, or
two or more of them may be used in an optional combination and
ratio.
[0154] The nitriding treatment is carried out by heating the
phosphor raw material in a state where the hydrogen-containing
nitrogen gas is filled or is permitted to flow, and the pressure at
that time may be slightly lower than the atmospheric pressure, or
equal or higher than the atmospheric pressure. However, to prevent
inclusion of oxygen in the atmospheric air, the pressure is
preferably at least the atmospheric pressure. If the pressure is
lower than the atmospheric pressure, if the air tightness of the
heating furnace is poor, a large amount of oxygen will be included,
whereby it may be difficult to obtain a phosphor having good
properties. The pressure of the hydrogen-containing nitrogen gas is
preferably at least 0.1 MPa (at least ordinary pressure) by gauge
pressure. Otherwise, it is also possible to carry out the heating
under a high pressure of at least 20 MPa. The pressure is
preferably at most 200 MPa. Thereafter, a gas containing nitrogen
is permitted to flow to sufficiently replace the inside of the
system with this gas. As the case requires, after evacuating the
inside of the system, the gas may be introduced.
[0155] By the way, the nitriding reaction of a metal is usually an
exothermic reaction. Accordingly, during the production of a
phosphor by an alloying method, it is possible that due to a
reaction heat discharged abruptly, the alloy is re-melted, and the
surface area decreases. If the surface area decreases like this,
the reaction between the nitrogen gas and the alloy may be delayed.
For this reason, in the alloying method, it is preferred to
maintain the reaction rate at which the alloy will not be melted,
so that a high performance phosphor can constantly be produced.
Particularly, it is preferred to carry out the firing by raising
the temperature at a low rate of at most 1.5.degree. C./min at
least in a temperature region of the rising of the exothermic peak
in the firing temperature region of from 1,150 to 1,400.degree. C.
where the heat generation of the nitriding is vigorous. The upper
limit in the temperature-raising rate is usually at most
1.5.degree. C./min, preferably at most 0.5.degree. C./min, more
preferably at most 0.1.degree. C./min. Further, the lower limit is
not particularly limited and may be determined from the economical
viewpoint for industrial production. Here, the exothermic peak is
an exothermic peak obtainable by TG-DTA
(thermogravimetry/differential thermal analysis).
[0156] By this method, it is possible to suppress abrupt generation
of the nitriding heat of the alloy and it is possible to suppress a
local temperature rise and to obtain a good phosphor, and at the
same time, by setting a high temperature raising rate in another
temperature region where no nitriding heat is generated, it is
possible to accomplish efficient production of a phosphor wherein
the overall firing time is shortened.
[0157] Further, the heating temperature varies also depending upon
e.g. the composition of the alloy for production of a phosphor, but
it is usually at least 1,000.degree. C. and at most 1,800.degree.
C., more preferably at least 1,400.degree. C. and at most
1,700.degree. C. Here, the temperature means the temperature in the
furnace during the heat treatment, i.e. the set temperature of the
firing apparatus.
[0158] In a case where a phosphor is prepared by nitriding an
alloy, heretofore, no flux was added at the stage of nitriding the
alloy, and after nitriding the alloy, particles were grown in the
presence of a flux at the time of the second firing. Advantages of
the nitriding the alloy in the presence of a flux in the present
invention will be described. Firstly, this nitride phosphor easily
loses luminance if oxygen is included during the preparation, but
by limiting the firing to once, it is possible to prevent inclusion
of oxygen by oxidation of an instable byproduct due to contact with
the atmospheric air. Secondly, melting or partial evaporation of
the flux during the firing will bring about the effect to reduce
the nitriding heat of the alloy thereby to suppress a local
temperature rise and contribute to the synthesis of good phosphor
particles. Thirdly, crystal growth will start in the presence of
the flux from the nitrided portion, whereby efficient crystal
growth will be accomplished, such being advantageous for high
luminance.
[0159] The heating time (retention time at the maximum temperature)
for the nitriding treatment may be a time required for the reaction
between the phosphor raw material and nitrogen, and it is usually
at least 1 minute, preferably at least 10 minutes, more preferably
at least 30 minutes, further preferably at least 60 minutes. If the
heating time is shorter than 1 minute, the nitriding reaction may
not be completed, and a phosphor having good properties may not be
obtained. Here, the upper limit for the heating time is determined
from the viewpoint of the production efficiency, and it is usually
at most 50 hours, preferably at most 24 hours.
[0160] In the production method of the present invention, as the
case requires, the alloy for production of a phosphor may
preliminarily be nitrided (primary nitriding), and then, the
above-described nitriding treatment may be carried out.
Specifically, the preliminary nitriding may be carried out by
heating the alloy for production of a phosphor in a
nitrogen-containing atmosphere for a prescribed time in a
prescribed temperature region. By introducing such a primary
nitriding step, it becomes possible to control the reactivity
between the alloy and nitrogen in the subsequent nitriding
treatment, and it is possible to industrially facilitate the
production of the phosphor from the alloy.
[0161] Further, the nitriding treatment may be carried out
repeatedly in a plurality of times, as the case requires. In such a
case, the conditions for the first firing (primary firing) and the
firing conditions for the second firing (secondary firing) and
subsequent firings are as described above, respectively. The
conditions for the second and subsequent firings may be set to be
the same or different from the conditions for the primary firing.
By applying the nitriding treatment to the phosphor raw material in
such a manner, it is possible to obtain the phosphor of the present
invention wherein a nitride or oxynitride is a matrix.
[2-4. Post Treatments]
[0162] In the production method of the present invention, in
addition to the above-described steps, other steps may be carried
out as the case requires. For example, after the above-described
firing step, a pulverization step, a cleaning step, a
classification step, a surface treatment step, a drying step, etc.
may be carried out, as the case requires.
[2-4-1. Pulverization Step]
[0163] In the pulverization, a pulverizer such as a hammer mill, a
roll mill, a ball mill, a jet mill, a ribbon blender, a V-type
blender or a Henschel mixer, or pulverization by means of a mortar
and a muddler may, for example, be used. At that time, in order to
suppress destruction of the formed phosphor crystals and to proceed
with treatment for the purpose of e.g. disintegrating secondary
particles, it is preferred that into a container made of e.g.
alumina, silicon nitride, ZrO.sub.2 or glass, balls made of the
same material as such or made of iron-core polyurethane are put,
and ball mill treatment is carried out for from 10 minutes to 24
hours. In such a case, a dispersing agent such as an alkali
phosphate of an organic acid or hexamethaphosphoric acid may be
used in an amount of from 0.05 wt % to 2 wt %.
[2-4-2. Cleaning Step]
[0164] The cleaning step may be carried out, for example, by water
such as deionized water, an organic solvent such as ethanol, or an
alkaline aqueous solution such as aqueous ammonia. For the purpose
of removing an impurity phase deposited on the surface of the
phosphor, such as to remove the used flux, thereby to improve the
emission properties, it is also possible to use an acidic aqueous
solution containing an inorganic acid such as hydrochloric acid,
nitric acid, sulfuric acid, aquaregia or a mixture of hydrofluoric
acid and sulfuric acid, or an organic acid such as acetic acid.
[0165] For the purpose of removing an amorphous content being an
impurity phase, an acidic aqueous solution containing e.g.
hydrofluoric acid, ammonium fluoride (NH.sub.4F), ammonium hydrogen
fluoride (NH.sub.4HF.sub.2), sodium hydrogen fluoride or potassium
hydrogen fluoride, may be used. Among them, a NH.sub.4HF.sub.2
aqueous solution is preferred. The concentration of the
NH.sub.4HF.sub.2 aqueous solution is usually from 1 wt % to 30 wt
%, preferably from 5 wt % to 25 wt %. Further, as the case
requires, these reagents may suitably be mixed for use.
[0166] Further, after the cleaning treatment with an alkaline
aqueous solution or an acidic aqueous solution, it is preferred to
carry out further cleaning with water. By such a cleaning step, it
is possible to improve the luminance, emission intensity,
absorption efficiency and object color of the phosphor.
[0167] In an example of the cleaning step, a fired product after
cleaning is stirred for 1 hour in a 10 wt % NH.sub.4HF.sub.2
aqueous solution in an amount 10 times by weight ratio, then
dispersed in water and then left to stand still for 1 hours, so
that cleaning is preferably carried out to such an extent that the
pH of the supernatant will be neutral (about pH 5 to 9). If the
above supernatant is deviated to basic or acidic, when it is mixed
with the after-mentioned liquid medium or the like, it may
adversely affect the liquid medium or the like.
[0168] In order to remove an impurity formed during the acid
cleaning, preferred is a method of carrying out cleaning with a
second liquid after cleaning with a first liquid, or a method of
cleaning with a liquid having two or more substances mixed. As an
example of the former, a process may be mentioned wherein cleaning
with a NH.sub.4HF.sub.2 aqueous solution is followed by cleaning
with hydrochloric acid and finally by washing with water. As an
example of the latter, a process may be mentioned wherein cleaning
with a mixed aqueous solution of NH.sub.4HF.sub.2 and HNO.sub.3, is
followed by washing with water.
[0169] The degree of the above cleaning may be represented by an
electrical conductivity of the supernatant obtained by dispersing
the phosphor after the cleaning in water 10 times by weight ratio,
followed by being left to stand still for 1 hour. Such an
electrical conductivity should better be low from the viewpoint of
the emission properties, but when also the productivity is taken
into consideration, it is preferred to carry out the cleaning
treatment repeatedly until it becomes usually at most 10 mS/m,
preferably at most 5 mS/m, more preferably at most 4 mS/m.
[0170] For the electrical conductivity, the phosphor is dispersed
by stirring in water 10 times by weight for a prescribed time (e.g.
10 minutes), then left to stand still for 1 hour to let particles
having heavier specific gravity than water be naturally
precipitated, whereupon the electrical conductivity of the
supernatant may be measured by means of e.g. an electrical
conductivity meter "EC METE CM-30G" manufactured by DKK-TOA
Corporation. Water to be used for the cleaning treatment or the
measurement of the electrical conductivity is not particularly
limited, but demineralized water or distilled water is preferred.
One having low electrical conductivity is particularly preferred,
and one having an electrical conductivity of usually at least
0.0064 mS/m and usually at most 1 mS/m, preferably at most 0.5
mS/m, is used. Here, the measurement of the electrical conductivity
is carried out usually at room temperature (about 25.degree.
C.).
[2-4-3. Classification Step]
[0171] The classification step can be carried out, for example, by
water sieving or by means of various classifiers such as various
air flow classifiers or shaking sieves. It is particularly
preferred to employ a dry system classification by means of nylon
mesh, whereby it is possible to obtain a phosphor having good
dispersibility having a weight median diameter of about 10
.mu.m.
[0172] Further, it is preferred to use the dry system
classification by means of nylon mesh and water sieving treatment
in combination, whereby it is possible to obtain a phosphor having
good dispersibility having a weight median diameter of about 20
.mu.m. Here, water sieving or water sieving treatment is usually
capable of dispersing phosphor particles at a concentration of from
0.1 wt % to 10 wt % in an aqueous medium. Further, in order to
suppress modification of the phosphor, the pH of the aqueous medium
is adjusted usually at least 4, preferably at least 5 and usually
at most 9, preferably at most 8. Further, at the time of obtaining
phosphor particles having the above-mentioned weight median
diameter, in the water sieving and hydraulic elutriation treatment,
it is preferred to carry out the sieving treatment in two steps
e.g. particles of at most 50 .mu.m are obtained, and then particles
of at most 30 .mu.m are obtained, from the viewpoint of the balance
of the operation efficiency and yield. Further, it is preferred to
carry out sieving treatment wherein the lower limit is usually at
least 1 .mu.m, preferably at least 5 .mu.m.
[2-4-4. Surface Treatment Step]
[0173] At the time of producing a light-emitting device by using
the phosphor of the present invention, in order to further improve
the weather resistance such as moisture resistance or to improve
the dispersibility in a resin in the after-mentioned
phosphor-containing portion of the light-emitting device, surface
treatment such as covering the surface of the phosphor with a
different material, may be carried out as the case requires.
[0174] The material which may be present on the surface of the
phosphor (hereinafter sometimes referred to as "a surface treatment
material") may, for example, be an organic compound, an inorganic
compound and a glass material.
[0175] The organic compound may, for example, be a heat meltable
polymer such as an acrylic resin, a polycarbonate, a polyamide or a
polyethylene, a latex, or a polyorganosiloxane.
[0176] The inorganic compound may, for example, be a metal oxide
such as magnesium oxide, aluminum oxide, silicon oxide, titanium
oxide, zirconium oxide, tin oxide, germanium oxide, tantalum oxide,
niobium oxide, vanadium oxide, boron oxide, antimony oxide, zinc
oxide, yttrium oxide or bismuth oxide, a metal nitride such as
silicon nitride or aluminum nitride, an orthophosphate such as
calcium phosphate, barium phosphate or strontium phosphate, a
polyphosphate, or a combination of a phosphate of an alkali metal
and/or alkaline earth metal with a calcium salt such as a
combination of sodium phosphate with calcium nitrate.
[0177] The glass material may, for example, be a borosilicate, a
phoshosilicate or an alkali metal silicate. One of such surface
treatment materials may be used alone, or two or more of them may
be used in an optional combination and ratio.
[0178] In the phosphor of the present invention obtainable by the
above surface treatment, the presence of the surface treatment
material is prerequisite, and the following may, for example, be
mentioned as the embodiments. (i) An embodiment wherein the above
surface treatment material constitutes a continuous film to cover
the surface of the phosphor. (ii) An embodiment wherein the above
surface treatment material is deposited on the surface of the
phosphor in the form of numeral fine particles to cover the surface
of the phosphor.
[0179] The deposition amount or covering amount of the surface
treatment material on the surface of the phosphor is optional so
long as the effects of the present invention are not substantially
thereby impaired, but it is usually at least 0.1 wt %, preferably
at least 1 wt %, more preferably at least 5 wt %, further
preferably at least 10 wt % and usually at most 50 wt %, preferably
at most 30 wt %, more preferably at most 20 wt %, based on the
weight of the phosphor. If the amount of the surface treatment
material is too much to the phosphor, the emission properties of
the phosphor may be impaired, and if it is too little, the surface
coverage tends to be incomplete, and no improvement of the moisture
resistance or dispersibility may be observed.
[0180] The film thickness (layer thickness) of the surface
treatment material to be formed by the surface treatment is
optional so long as the effects of the present invention are not
substantially thereby impaired, but it is usually at least 10 nm,
preferably at least 50 nm and usually at most 2,000 nm, preferably
at most 1,000 nm. If this film thickness of too thick, the emission
properties of the phosphor may be impaired, and if it is too thin,
the surface coverage tends to be inadequate, and no improvement of
the moisture resistance or dispersibility may be observed.
[0181] The method for the surface treatment is not particularly
limited, and for example, a coverage treatment method by the
following metal oxide (silicon oxide) may be mentioned.
[0182] The phosphor of the present invention is mixed in an alcohol
such as ethanol and stirred, and further, an alkaline aqueous
solution such as aqueous ammonia is mixed and stirred. Then, a
hydrolyzable alkyl silicic acid ester such as
tetraethylorthosilicic acid is mixed and stirred. The obtained
solution is left to stand for from 3 minutes to 60 minutes,
whereupon the supernatant containing silicon oxide particles not
deposited on the surface of the phosphor, is removed by e.g. a
dropper. Then, the mixing of an alcohol, stirring, being left to
stand still and removal of the supernatant, are repeated a few
times, and then, via a reduced pressure drying step at from
120.degree. C. to 150.degree. C. for from 10 minutes to 5 hours,
e.g. 2 hours, the surface treated phosphor is obtained.
[0183] As the method for surface treatment of the phosphor, a known
method may further be used, such as a method of depositing e.g.
spherical silicon oxide fine powder on the phosphor (JP-A-2-209989,
JP-A-2-233794), a method of depositing a coating film of a
silicon-type compound on the phosphor (JP-A-3-231987), a method of
covering the surface of fine particles of a phosphor with fine
particles of a polymer (JP-A-6-314593), a method of coating a
phosphor with an organic material, an inorganic material and glass
material, etc. (JP-A-2002-223008), a method of covering the surface
of a phosphor by a chemical vapor phase reaction method
(JP-A-2005-82788), or a method of depositing particles of a metal
compound (JP-A-2006-28458).
[3. Phosphor-Containing Composition]
[0184] The phosphor-containing composition of the present invention
comprises the phosphor of the present invention and a liquid
medium. In a case where the phosphor of the present invention is
used for an application to e.g. a light-emitting device, it is
preferred to use it in a form dispersed in a liquid medium i.e. in
a form of a phosphor-containing composition.
[0185] As the liquid medium useful for the phosphor-containing
composition of the present invention, an optional one may be
selected for use depending upon the purpose, so long as it shows a
liquid nature under the desired application conditions and so long
as the phosphor of the present invention can suitably be dispersed
therein, and no undesirable reaction or the like will take place.
Examples of such a liquid medium include a silicone resin, an epoxy
resin, a polyvinyl resin, a polyethylene resin, a polypropylene
resin, a polyester resin, etc. One of such liquid media may be used
alone, or two or more of them may be used in an optional
combination and ratio. Further, an organic solvent may be
incorporated to the above liquid medium.
[0186] The amount of the liquid medium to be used may suitably be
adjusted depending upon the particularly application, but usually,
it is within a range of usually at least 3 wt %, preferably at
least 5 wt % and usually at most 30 wt %, preferably at most 15 wt
%, by the weight ratio of the liquid medium to the phosphor of the
present invention. If the liquid medium is too little, the amount
of luminescence from the phosphor-containing composition per volume
tends to be low, and if it is too much, the dispersibility of the
phosphor powder tends to be poor, and color unevenness tends to
occur.
[0187] The phosphor-containing composition of the present invention
may contain, in addition to the phosphor of the present invention
and the liquid medium, other optional components depending upon the
particular application, etc. As such other components, a diffusing
agent, a thickener, a filler, an interfering agent, etc. may be
mentioned. Specifically, a silica type fine powder such as aerosol,
alumina or the like may be mentioned. One of such other components
may be used alone, or two or more of them may be used in an
optional combination and ratio.
[0188] In a case where the phosphor-containing composition is used
as a constituting component of a light-emitting device (e.g. the
after-descried second illuminant), the phosphor-containing
composition can be made to be the above constituting component by
curing the liquid medium.
[4. Light-Emitting Device]
[0189] Now, the light-emitting device of the present invention will
be described. The light-emitting device of the present invention is
a light-emitting device having a first illuminant and a second
illuminant which emits visible light under irradiation with light
from the first illuminant, wherein as the second illuminant, a
first phosphor is contained, which contains at least one phosphor
of the present invention.
[4-1. First Illuminant]
[0190] The first illuminant in the light-emitting device of the
present invention is one which emits light to excite the
after-described second illuminant. The emission wavelength of the
first illuminant is not particularly limited so long as it is one
which overlaps with the absorption wavelength of the
after-described second illuminant, and illuminants within a wide
emission wavelength region can be used. Further, as the first
illuminant to be suitably used, for example, one having an emission
peak within a wavelength range of from 300 nm to 420 nm, one having
an emission peak within a wavelength range of from 420 to 450 nm,
or one having an emission peak within a wavelength range of from
420 nm to 500 nm, may, for example, be mentioned.
[0191] Usually, an illuminant having an emission wavelength within
a range of from a near ultraviolet region to a blue color region is
used, and as a specific numerical value, an illuminant having an
emission wavelength of usually at least 300 nm, preferably at least
330 nm and usually at most 500 nm, preferably at most 480 nm, is
used.
[0192] As such a first illuminant, a semiconductor light-emitting
element is usually employed. Specifically, a light-emitting diode
(LED) or a semiconductor laser diode (hereinafter sometimes
referred to simply as "LD") may, for example, be used.
[0193] Among them, as the first illuminant, a GaN type LED or LD
using a GaN type compound semiconductor is preferred. Because, the
GaN type LED or LD has a remarkably large emission output or
external quantum efficiency as compared with a SiC type LED or the
like which emits light in this region, and by combining it with the
above phosphor, it is possible to obtain very bright emission of
light with a very low electric power. For example, to a current
load of 20 mA, the GaN type LED or LD usually has an emission
intensity at a level of at least 100 times that of the SiC type. In
the GaN type LED or LD, one having an Al.sub.XGa.sub.YN
light-emitting layer, a GaN light-emitting layer or an
In.sub.XGa.sub.YN light-emitting layer is preferred. In the GaN
type LED, one having an In.sub.XGa.sub.YN light-emitting layer is
particularly preferred among them, since the emission intensity is
very high. In the GaN type LD, one having a multiple quantum well
structure of an In.sub.XGa.sub.YN layer and a GaN layer is
particularly preferred, since the emission intensity is very
high.
[0194] Here, in the above description, the value of X+Y is usually
a value within a range of from 0.8 to 1.2. In the GaN type LED, one
having Zn or Si doped to such a light-emitting layer or one having
no dopant is preferred for adjustment of the emission
properties.
[0195] The GaN type LED is one comprising such a light-emitting
layer, a p-layer, a n-layer, electrodes and an substrate, as basic
structural elements, and one having a hetero structure wherein a
light-emitting layer is sandwiched between n-type and p-type
Al.sub.XGa.sub.YN layers, GaN layers or In.sub.XGa.sub.YN layers is
preferred, since the luminous efficiency is high. Further, one
having such a hetero structure made into a quantum well structure
is more preferred, since the luminous efficiency is higher. Such
LED or LD is already commercialized and readily available.
[4-2. Second Illuminant]
[0196] The second illuminant in the light-emitting device of the
present invention is an illuminant which emits visible light under
irradiation with light from the above-described first illuminant,
and it contains a first phosphor (the phosphor of the present
invention) and at the same time, may suitably contain a second
phosphor depending upon the particular application, etc. Further,
the second illuminant is, for example, constituted by dispersing
the first and/or second phosphor in a sealing material.
[4-2-1. First Phosphor]
[0197] In the light-emitting device of the present invention, the
second illuminant is one containing the above-described phosphor of
the present invention, and contains, as a first phosphor, at least
one phosphor of the present invention. Further, as the first
phosphor, in addition to the phosphor of the present invention, a
phosphor which emits fluorescence of the same color as the phosphor
of the present invention (hereinafter sometimes referred to as "the
same color concomitant phosphor") may be used at the same time.
Usually, the phosphor of the present invention is a yellow
phosphor, and as the first phosphor, together with the phosphor of
the present invention, another type of yellow to orange phosphor
(the same color concomitant phosphor) may be used in
combination.
[0198] The same color concomitant phosphor may, for example, be
Y.sub.3Al.sub.5O.sub.12:Ce, or Eu-activated M.sub.x (Si,
Al).sub.12(O, N).sub.16 (wherein M is a metal element such as Ca or
Y, and x is one obtained by dividing the number of moles of the
oxygen atom by the average valency of M, and the number of moles of
the oxygen atom is usually larger than 0 and at most 4.3). Here,
one of these may be used alone, or two or more of them may be used
in an optional combination and ratio.
[0199] The emission peak wavelength .lamda..sub.p (nm) of the same
color concomitant phosphor is not particularly limited, but it is
within a wavelength range of usually at least 500 nm, preferably at
least 520 nm, and usually at most 650 nm, preferably at most 630
nm. If the emission peak wavelength of the first phosphor is too
short or too long, it tends to be difficult to obtain a good white
color in the combination with the first illuminant or with the
second phosphor.
[0200] The full width at half maximum (FWHM) of the emission peak
of the same color concomitant phosphor is not limited, but it is
usually at least 110 nm, preferably at least 120 nm and usually at
most 280 nm. If this full width at half maximum is too narrow, the
color rendering property is likely to be low.
[0201] In a case where as the first phosphor, the phosphor of the
present invention and another phosphor (the same color concomitant
phosphor) are used, the ratio of the two is optional so long as the
effects of the present invention are not substantially thereby
impaired. However, the ratio of the phosphor of the present
invention should better be large. Specifically, the ratio of the
phosphor of the present invention in the entire first phosphor is
usually at least 40 wt %, preferably at least 60 wt %, more
preferably at least 70 wt %. However, it is particularly preferred
to use only the phosphor of the present invention as the first
phosphor.
[4-2-2. Second Phosphor]
[0202] The second illuminant in the light-emitting device of the
present invention may contain, in addition to the above-described
first phosphor, another phosphor (i.e. a second phosphor). This
second phosphor is a phosphor having an emission wavelength
different from the first phosphor. Usually, such a second phosphor
is used to adjust the emission color of the second illuminant, and
therefore, as the second phosphor, a phosphor to emit fluorescence
of a color different from the first phosphor, is used in many
cases.
[0203] As mentioned above, as the first phosphor, the phosphor of
the present invention is usually used, and therefore, as the second
phosphor, it is preferred to use, for example, a phosphor having an
emission peak within a wavelength range of from 565 nm to 780 nm
(hereinafter sometimes referred to as "an orange or red phosphor"),
a phosphor having an emission peak within a wavelength of from 420
nm to 500 nm (hereinafter sometimes referred to as "a blue
phosphor"), or a phosphor having an emission peak within a
wavelength range of from 500 nm to 550 nm (hereinafter sometimes
referred to as "a green phosphor").
[0204] Further, as the second phosphor, one phosphor may be used
alone, or two or more phosphors may be used in an optional
combination and ratio. Further, the ratio of the second phosphor to
the first phosphor is also optional unless the effects of the
present invention are not substantially impaired. Accordingly, the
amount of the second phosphor to be used as well as the combination
of phosphors to be used as the second phosphor and their ratio may
optionally be set depending upon the particular application of the
light-emitting device, etc. Now, the second phosphor will be
described in further detail.
[4-2-2-1. Orange or Red Phosphor]
[0205] The emission peak wavelength of the orange or red phosphor
is preferably within a wavelength range of usually at least 565 nm,
preferably at least 575 nm, more preferably at least 580 nm and
usually at most 780 nm, preferably at most 700 nm, more preferably
at most 680 nm.
[0206] Such an orange or red phosphor may, for example, be a
europium-activated alkaline earth silicon nitride phosphor
represented by (Mg,Ca,Sr,Ba).sub.2Si.sub.5N.sub.8:Eu, which is
constituted by fractured particles having a red fracture surface
and which emits light in a red color region, or a
europium-activated rare earth oxychalcogenide phosphor represented
by (Y,La,Gd,Lu).sub.2O.sub.2S:Eu, which is constituted by grown
particles having substantially a spherical shape as a regular
crystal-growth shape and which emits light in a red color
region.
[0207] The full width at half maximum of the emission peak of the
red phosphor is usually within a range of from 1 nm to 100 nm.
Further, the external quantum efficiency is usually at least 60%,
preferably at least 70%, and the weight median diameter is usually
at least 1 .mu.m, preferably at least 5 .mu.m, further preferably
at least 10 .mu.m and usually at most 30 .mu.m, preferably at most
20 .mu.m, further preferably at most 15 .mu.m.
[0208] Further, a phosphor containing an oxynitride and/or
oxysulfide containing at least one element selected from the group
consisting of Ti, Zr, Hf, Nb, Ta, W and Mo, as disclosed in
JP-A-2004-300247, which contains an oxynitride having an
.alpha.-SiAlON structure having a part or all of Al element
substituted by Ga element, may also be used in the present
invention.
[0209] Further, as the red phosphor, it is possible to use, for
example, an Eu-activated oxysulfide phosphor such as
(La,Y).sub.2O.sub.2S:Eu, an Eu-activated oxide phosphor such as
Y(V,P)O.sub.4:Eu or Y.sub.2O.sub.3:Eu, Eu, Mn-activated silicate
phosphor such as (Ba,Mg).sub.2SiO.sub.4:Eu,Mn, or
(Ba,Sr,Ca,Mg).sub.2SiO.sub.4:Eu,Mn, an Eu-activated tungstenate
phosphor such as LiW.sub.2O.sub.8:Eu, LiW.sub.2O.sub.8:Eu,Sm,
Eu.sub.2W.sub.2O.sub.9, Eu.sub.2W.sub.2O.sub.9:Nb, or
Eu.sub.2W.sub.2O.sub.9:Sm, an Eu-activated sulfide phosphor such as
(Ca,Sr)S:Eu, an Eu-activated aluminate phosphor such as
YAlO.sub.3:Eu, an Eu-activated silicate phosphor such as
Ca.sub.2Y.sub.8(SiO.sub.4).sub.8O.sub.2:Eu,
LiY.sub.9(SiO.sub.4).sub.6O.sub.2:Eu, (Sr,Ba,Ca).sub.3SiO.sub.5:Eu,
or Sr.sub.2BaSiO.sub.5:Eu, a Ce-activated aluminate phosphor such
as (Y,Gd).sub.3Al.sub.5O.sub.12:Ce, or
(Tb,Gd).sub.3Al.sub.5O.sub.12:Ce, an Eu-activated oxide, nitride or
oxynitride phosphor such as
(Mg,Ca,Sr,Ba).sub.2Si.sub.5(N,O).sub.8:Eu,
(Mg,Ca,Sr,Ba)Si(N,O).sub.2:Eu, or (Mg,Ca,Sr,Ba)AlSi(N,O).sub.3:Eu,
an Eu,Mn-activated halophosphate phosphor such as
(Sr,Ca,Ba,Mg).sub.10(PO.sub.4).sub.6Cl.sub.2:Eu,Mn, an
Eu,Mn-activated silicate phosphor such as
Ba.sub.3MgSi.sub.2O.sub.8:Eu,Mn, or
(Ba,Sr,Ca,Mg).sub.3(Zn,Mg)Si.sub.2O.sub.8:Eu,Mn, a Mn-activated
germinate phosphor such as 3.5MgO.0.5MgF.sub.2.GeO.sub.2:Mn, an
Eu-activated oxynitride phosphor such as an Eu-activated
.alpha.-SiAlON, an Eu,Bi-activated oxide phosphor such as
(Gd,Y,Lu,La).sub.2O.sub.3:Eu,Bi, an Eu,Bi-activated oxysulfie
phosphor such as (Gd,Y,Lu,La).sub.2O.sub.2S:Eu,Bi, an
Eu,Bi-activated vanadinate phosphor such as
(Gd,Y,Lu,La)VO.sub.4:Eu,Bi, an Eu, Ce-activated sulfide phosphor
such as SrY.sub.2S.sub.4:Eu, Ce, a Ce-activated sulfide phosphor
such as CaLa.sub.2S.sub.4:Ce, an Eu,Mn-activated phosphate phosphor
such as (Ba,Sr,Ca)MgP.sub.2O.sub.7:Eu,Mn, or
(Sr,Ca,Ba,Mg,Zn).sub.2P.sub.2O.sub.7:Eu,Mn, an Eu,Mo-activated
tungstate phosphor such as (Y,Lu).sub.2WO.sub.6:Eu,Mo, an Eu,
Ce-activated nitride phosphor such as
(Ba,Sr,Ca).sub.xSi.sub.yN.sub.z:Eu, Ce (wherein each of x, y and z
is an integer of at least 1), an Eu,Mn-activated halophosphate
phosphor such as
(Ca,Sr,Ba,Mg).sub.10(PO.sub.4).sub.6(F,Cl,Br,OH):Eu,Mn, or a
Ce-activated silicate phosphor such as
((Y,Lu,Gd,Tb).sub.1-x-ySc.sub.xCe.sub.y).sub.2(Ca,Mg).sub.1-r(Mg,Zn).sub.-
2+rSi.sub.z-qGe.sub.qO.sub.12+.delta..
[0210] As the red phosphor, it is also possible to use a red
organic phosphor made of a rare earth element ion complex having,
as a ligand, an anion such as a .beta.-diketonate, a
.beta.-diketone, an aromatic carboxylic acid or a Bronsted acid, a
perylene pigment (such as
dibenzo{[f,f']-4,4',7,7'-tetraphenyl}diindeno[1,2,3-cd:1',2',3'-lm]peryle-
ne), an anthraquinone pigment, a lake pigment, an azo pigment, a
quinacridone pigment, an anthracene pigment, an isoindoline
pigment, an isoindolinone pigment, a phthalocyanine pigment, a
triphenylmethane basic dye, an indanthrone pigment, an indophenol
pigment, a cyanine pigment or a dioxazine pigment.
[0211] Among the above, the red phosphor preferably contains
(Ca,Sr,Ba).sub.2Si.sub.5(N,O).sub.8:Eu, (Ca,Sr,Ba)Si(N,O).sub.2:Eu,
(Ca,Sr,Ba)AlSi(N,O).sub.3:Eu, (Ca,Sr,Ba)AlSi(N,O).sub.3:Ce,
(Sr,Ba).sub.3SiO.sub.5:Eu, (Ca,Sr)S:Eu, (La,Y).sub.2O.sub.2S:Eu or
an Eu complex. More preferably, it contains
(Ca,Sr,Ba).sub.2Si.sub.5(N,O).sub.8:Eu, (Ca,Sr,Ba)Si(N,O).sub.2:Eu,
(Ca,Sr,Ba)AlSi(N,O).sub.3:Eu, (Ca,Sr,Ba)AlSi(N,O).sub.3:Ce,
(Sr,Ba).sub.3SiO.sub.5:Eu, (Ca,Sr)S:Eu or (La,Y).sub.2O.sub.2S:Eu,
or a .beta.-diketone type Eu complex such as an Eu
(dibenzoylmethane)3.1,10-phenanthroline complex, or a carboxylic
acid type Eu complex. Particularly preferred is
(Ca,Sr,Ba).sub.2Si.sub.5(N,O).sub.8:Eu, (Sr,Ca)AlSi(N,O):Eu or
(La,Y).sub.2O.sub.2S:Eu.
[0212] Further, in the above exemplification, as the orange
phosphor, (Sr,Ba).sub.3SiO.sub.5:Eu is preferred. One of such
orange or red phosphors may be used alone, or two or more of them
may be used in an optional combination and ratio.
[4-2-2-2. Blue Phosphor]
[0213] The emission peak wavelength of the blue phosphor is
preferably within a range of usually at least 420 nm, preferably at
least 430 nm, more preferably at least 440 nm and usually at most
500 nm, preferably at most 480 nm, more preferably at most 470 nm,
further preferably at most 460 nm.
[0214] The full width at half maximum of the emission peak of the
blue phosphor is usually within a range of from 20 nm to 80 nm.
Further, the external quantum efficiency is usually at least 60%,
preferably at least 70%, and the weight median diameter is usually
at least 1 .mu.m, preferably at least 5 .mu.m, further preferably
at least 10 .mu.m and usually at most 30 .mu.m, preferably at most
20 .mu.m, more preferably at most 15 .mu.m.
[0215] Such a blue phosphor may, for example, be a
europium-activated barium magnesium aluminate phosphor represented
by Ba,Sr, Ca)MgAl.sub.10O.sub.17:Eu constituted by grown particles
having a substantially hexagonal shape as a regular crystal growth
shape and which emits light in a blue region, a europium-activated
calcium halophosphate phosphor represented by
(Mg,Ca,Sr,Ba).sub.5(PO.sub.4).sub.3(Cl,F):Eu which is constituted
by grown particles having a substantially spherical shape as a
regular crystal growth shape and which emits light in a blue
region, a europium-activated alkaline earth chloroborate phosphor
represented by (Ca,Sr,Ba).sub.2B.sub.5O.sub.9Cl:Eu which is
constituted by grown particles having a substantially cubic shape
as a regular crystal growth shape and which emits light in a blue
region or a europium-activated alkaline earth aluminate phosphor
represented by (Sr,Ca,Ba)Al.sub.2O.sub.4:Eu or
(Sr,Ca,Ba).sub.4Al.sub.14O.sub.25:Eu, which is constituted by
fractured particles having a fracture surface and which emits light
in a bluish green region.
[0216] Further, as the blue phosphor, it is possible to use a
Sn-activated phosphate phosphor such as Sr.sub.2P.sub.2O.sub.7:Sn,
an Eu-activated aluminate phosphor such as
(Sr,Ca,Ba)Al.sub.2O.sub.4:Eu or
(Sr,Ca,Ba).sub.4Al.sub.14O.sub.25:Eu, BaMgAl.sub.10O.sub.17:Eu,
(Ba,Sr,Ca)MgAl.sub.10O.sub.17:Eu, BaMgAl.sub.10O.sub.17:Eu, Tb,Sm,
BaAl.sub.8O.sub.13:Eu, a Ce-activated thiogalate phosphor such as
SrGa.sub.2S.sub.4:Ce, or CaGa.sub.2S.sub.4:Ce, an Eu,Mn-activated
aluminate phosphor such as (Ba,Sr,Ca)MgAl.sub.10O.sub.17:Eu,Mn, an
Eu-activated halophosphate phosphor such as
(Sr,Ca,Ba,Mg).sub.10(PO.sub.4).sub.6Cl.sub.2:Eu, or
(Ba,Sr,Ca).sub.5(PO.sub.4).sub.3(Cl,F,Br,OH):Eu,Mn,Sb, an
Eu-activated silicate phosphor such as
BaAl.sub.2Si.sub.2O.sub.8:Eu, or (Sr,Ba).sub.3MgSi.sub.2O.sub.8:Eu,
an Eu-activated phosphate phosphor such as
Sr.sub.2P.sub.2O.sub.7:Eu, a sulfide phosphor such as ZnS:Ag, or
ZnS:Ag,Al, a Ce-activated silicate phosphor such as
Y.sub.2SiO.sub.5:Ce, a tungstate phosphor such as CaWO.sub.4, an
Eu,Mn-activated borophosphate phosphor such as
(Ba,Sr,Ca)BPO.sub.5:Eu,Mn,
(Sr,Ca).sub.10(PO.sub.4).sub.8.nB.sub.2O.sub.3:Eu, or
2SrO.0.84P.sub.2O.sub.5.0.16B.sub.2O.sub.3:Eu, an Eu-activated
halosilicate phosphor such as
Sr.sub.2Si.sub.3O.sub.8.2SrCl.sub.2:Eu, an Eu-activated oxynitride
phosphor such as SrSi.sub.9Al.sub.19ON.sub.31:Eu, or
EuSi.sub.9Al.sub.19ON.sub.31, or a Ce-activated oxynitride phosphor
such as La.sub.1-xCe.sub.xAl(Si.sub.6-zAl.sub.z)(N.sub.10-zO.sub.z)
(wherein x and z are numbers which satisfy 0.ltoreq.x.ltoreq.1 and
0.ltoreq.z.ltoreq.6, respectively),
La.sub.1-x-yCe.sub.xCa.sub.yAl(Si.sub.6-zAl.sub.z)(N.sub.10-zO.sub.z)
(wherein x, y and z are numbers which satisfy 0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1 and 0.ltoreq.z.ltoreq.6, respectively),
etc.
[0217] Further, as the blue phosphor, it is also possible to use a
fluorescent pigment of a naphthalic acid imide type, benzoxazole
type, styryl type, coumarin type, pyrazoline type or triazole type
compound, or an organic phosphor such as a thulium complex.
[0218] In the above exemplification, the blue phosphor preferably
contains (Ca,Sr,Ba)MgAl.sub.10O.sub.17:Eu,
(Sr,Ca,Ba,Mg).sub.10(PO.sub.4).sub.6(Cl,F).sub.2:Eu or
(Ba,Ca,Mg,Sr).sub.2SiO.sub.4:Eu. More preferably, it contains
(Ca,Sr,Ba)MgAl.sub.10O.sub.17:Eu,
(Sr,Ca,Ba,Mg).sub.10(PO.sub.4).sub.8(Cl,F).sub.2:Eu or
(Ba,Ca,Sr).sub.3MgSi.sub.2O.sub.8:Eu. Further preferably, it
contains BaMgAl.sub.10O.sub.17:Eu,
Sr.sub.10(PO.sub.4).sub.6(Cl,F).sub.2:Eu or
Ba.sub.3MgSi.sub.2O.sub.8:Eu. Further, among them, for lighting
applications and display applications,
(Sr,Ca,Ba,Mg).sub.10(PO.sub.4).sub.6Cl.sub.2:Eu or
(Ca,Sr,Ba)MgAl.sub.10O.sub.17:Eu is particularly preferred.
Further, one of such blue phosphors may be used alone, or two or
more of them may be used in an optional combination and ratio.
[4-2-2=3. Green Phosphor]
[0219] The emission peak wavelength of the green phosphor is
preferably within a range of usually more than 500 nm, preferably
at least 510 nm, more preferably at least 515 nm and usually at
most 550 nm, preferably at most 540 nm, further preferably at most
535 nm. If this emission peak wavelength .lamda.p is too short, the
color tends to be bluish, and if it is too long, the color tends to
be yellowish, and thus in either case, the properties as green
light may be deteriorated.
[0220] The full width at half maximum of the emission peak of the
green phosphor is usually within a range of from 40 nm to 80 nm.
Further, the external quantum efficiency is usually at least 60%,
preferably at least 70%, and the weight median diameter is usually
at least 1 .mu.m, preferably at least 5 .mu.m, more preferably at
least 10 .mu.m and usually at most 30 .mu.m, preferably at most 20
.mu.m, more preferably at most 15 .mu.m.
[0221] A specific example of the green phosphor may, for example,
be a europium-activated alkaline earth silicon oxynitride phosphor
represented by (Mg,Ca,Sr,Ba)Si.sub.2O.sub.2N.sub.2:Eu which is
constituted by fractured particles having a fracture surface and
which emits light in a green region.
[0222] As other green phosphors, it is possible to use an
Eu-activated aluminate phosphor such as
Sr.sub.4Al.sub.14O.sub.25:Eu, or (Ba,Sr,Ca)Al.sub.2O.sub.4:Eu, an
Eu-activated silicate phosphor such as
(Sr,Ba)Al.sub.2Si.sub.2O.sub.8:Eu, (Ba,Mg).sub.2SiO.sub.4:Eu,
(Ba,Sr, Ca,Mg).sub.2SiO.sub.4:Eu,
(Ba,Sr,Ca).sub.2(Mg,Zn)Si.sub.2O.sub.7:Eu, or
(Ba,Ca,Sr,Mg).sub.9(Sc,Y,Lu,Gd).sub.2(Si,Ge).sub.6O.sub.24:Eu, a
Ce,Tb-activated silicate phosphor such as Y.sub.2SiO.sub.5:Ce,Tb,
an Eu-activated borophosphate phosphor such as
Sr.sub.2P.sub.2O.sub.7--Sr.sub.2B.sub.2O.sub.5:Eu, an Eu-activated
halosilicate phosphor such as
Sr.sub.2Si.sub.3O.sub.5-2SrCl.sub.2:Eu, a Mn-activated silica
phosphor such as Zn.sub.2SiO.sub.4:Mn, a Tb-activated aluminate
phosphor such as CeMgAl.sub.11O.sub.19:Tb, or
Y.sub.3Al.sub.5O.sub.12:Tb, a Tb-activated silica phosphor such as
Ca.sub.2Y.sub.8(SiO.sub.4).sub.6O.sub.2:Tb, or
La.sub.3Ga.sub.5SiO.sub.14:Tb, an Eu,Tb,Sm-activated thiogalate
phosphor such as (Sr,Ba,Ca)Ga.sub.2S.sub.4:Eu,Tb,Sm, a Ce-activated
aluminate phosphor such as Y.sub.3(Al,Ga).sub.5O.sub.12:Ce or
(Y,Ga,Tb,La,Sm,Pr,Lu).sub.3(Al,Ga).sub.5O.sub.12:Ce, a Ce-activated
silicate phosphor such as Ca.sub.3Sc.sub.2Si.sub.3O.sub.12:Ce, or
Ca.sub.3(Sc,Mg,Na,Li).sub.2Si.sub.3O.sub.12:Ce, a Ce-activated
oxide phosphor such as CaSc.sub.2O.sub.4:Ce, an Eu-activated
oxynitride phosphor such as an Eu-activated .beta.-SiAlON, an
Eu,Mn-activated aluminate phosphor such as
BaMgAl.sub.10O.sub.17:Eu,Mn, an Eu-activated aluminate phosphor
such as SrAl.sub.2O.sub.4:Eu, a Tb-activated oxysulfide phosphor
such as (La,Gd,Y).sub.2O.sub.2S:Tb, a Ce,Tb-activated phosphate
phosphor such as LaPO.sub.4:Ce,Tb, a sulfide phosphor such as
ZnS:Cu,Al, or ZnS:Cu,Au,Al, a Ce,Tb-activated borate phosphor such
as (Y,Ga,Lu,Sc,La)BO.sub.3:Ce,Tb,
Na.sub.2Gd.sub.2B.sub.2O.sub.7:Ce,Tb, or
(Ba,Sr).sub.2(Ca,Mg,Zn)B.sub.2O.sub.5:K,Ce,Tb, an Eu,Mn-activated
halosilicate phosphor such as
Ca.sub.5Mg(SiO.sub.4).sub.4Cl.sub.2:Eu,Mn, an Eu-activated
thioaluminate phosphor or thiogalate phosphor such as
(Sr,Ca,Ba)(Al,Ga,In).sub.2S.sub.4:Eu, an Eu,Mn-activated
halosilicate phosphor such as
(Ca,Sr).sub.8(Mg,Zn)(SiO.sub.4).sub.4Cl.sub.2:Eu,Mn, and an
Eu-activated oxynitride phosphor such as
M.sub.3Si.sub.6O.sub.9N.sub.4:Eu, M.sub.3Si.sub.6O.sub.12N.sub.2:Eu
(wherein M is an alkaline earth metal element).
[0223] Further, as the green phosphor, it is also possible to use a
pyridine-phthalimide condensation derivative, a fluorescent pigment
such as a benzoxazinone type, quinazolinone type, coumarin type,
quinophthalone type or naphthalic acid imido type, or an organic
phosphor such as a terbium complex. One of the above exemplified
green phosphors may be used alone, or two or more of them may be
used in an optional combination and ratio.
[4-2-3. Other Properties of First and Second Phosphors]
[0224] The weight median diameters of the first phosphor and the
second phosphor are optional so long as the effects of the present
invention are not substantially thereby impaired, but they are
preferably within a range of usually at least 0.1 .mu.m, preferably
at least 0.5 .mu.m and usually at most 30 .mu.m, preferably at most
20 .mu.m. If the weight median diameters are too small, the
luminance tends to be deteriorated, and the phosphor particles tend
to be agglomerated. On the other hand, if the weight median
diameters are too large, the coating unevenness or clogging of the
dispenser tends to occur.
[4-3. Combination of First Illuminant and First Phosphor and Second
Phosphor]
[0225] In the light-emitting device of the present invention, use
or non-use, or the type of the second phosphor (red phosphor, blue
phosphor, green phosphor, etc.) as described above, may suitably be
selected depending upon the particularly application of the
light-emitting device. For example, in a case where the first
phosphor is a yellow phosphor, when the light-emitting device of
the present invention is to be constructed as a light-emitting
device to emit a yellow color, only the first phosphor may be used,
and it is usually unnecessary to use the second phosphor.
[0226] On the other hand, it is possible to construct the
light-emitting device by suitably combining the first phosphor
(yellow phosphor) and the second phosphor, as phosphors contained
in the second illuminant, in order to obtain tight having a desired
color.
[0227] The following combinations (i) to (iv) may be mentioned as
examples of a preferred combination of the first illuminant, the
first phosphor and the second phosphor in the case of constructing
such a light-emitting device.
(i) As the first illuminant, a blue illuminant (such as short
wavelength blue LED) having an emission peak wavelength in a
wavelength range of from 420 nm to 450 nm is used, and as the first
phosphor, a yellow phosphor (such as the phosphor of the present
invention) is used. It is thereby possible to construct a
light-emitting device which emits a pseudo white color. (ii) As the
first illuminant, a blue illuminant (such as blue LED) having an
emission peak wavelength in a wavelength range of from 420 nm to
500 nm, is used; as the first phosphor, a yellow phosphor (such as
the phosphor of the present invention) is used; and as the second
phosphor, a red phosphor is used. It is thereby possible to
construct a light-emitting device which emits a light bulb color.
(iii) As the first illuminant, a near ultraviolet illuminant (such
as near ultraviolet LED) having an emission peak wavelength in a
wavelength range of from 300 nm to 420 nm, is used; as the first
phosphor, a yellow phosphor (such as the phosphor of the present
invention) is used, and as the second phosphor, a blue phosphor is
used. It is thereby possible to construct a light-emitting device
which emits a pseudo white color. (iv) As the first illuminant, a
near ultraviolet illuminant (such as near ultraviolet LED) having
an emission peak wavelength in a wavelength range of from 300 nm to
420 nm, is used; as the first phosphor, a yellow phosphor (such as
the phosphor of the present invention) is used; and as the second
phosphor, a blue phosphor, a green phosphor and a red phosphor are
used. It is thereby possible to construct a light-emitting device
which emits a light bulb color.
[4-4. Sealing Material]
[0228] In the light-emitting device of the present invention, the
first and/or second phosphor is employed usually by dispersing and
sealing it in a liquid medium being a sealing material, followed by
curing by heat or light. As the liquid medium, the same one as
disclosed in the above section [3. Phosphor-containing composition]
may be mentioned.
[0229] Further, the liquid medium may contain a metal element which
can be a metal oxide having a high refractive index in order to
adjust the refractive index of the sealing component. Si, Al, Zr,
Ti, Y, NB, B, etc. may be mentioned as examples for the metal
element which presents a metal oxide having a high refractive
index. One of these metal elements may be used alone, or two or
more of them may be used in an optional combination and ratio.
[0230] The form of such a metal element to be present is not
particularly limited so long as the transparency of the sealing
component is not impaired. For example, it may form a uniform glass
layer as a metalloxane bond or may be present in the form of
particles in the sealing component. When it is present in the form
of particles, the structure of the interior of the particles may be
amorphous or a crystal structure, but in order to present a high
refractive index, it is preferably a crystal structure. Further,
its particle diameter is usually at most the emission wavelength of
a semiconductor light-emitting element, preferably at most 100 nm,
more preferably at most 50 nm, particularly preferably at most 30
nm, in order not to impair the transparency of the sealing
component. For example, by mixing particles of silicon oxide,
aluminum oxide, zirconium oxide, titanium oxide, yttrium oxide,
niobium oxide or the like to a silicone material, it is possible to
let the above metal element be present in the form of particles in
the sealing component.
[0231] The above liquid medium may further contain known additives
such as a diffusing agent, a filler, a viscosity-controlling agent,
an ultraviolet absorber, etc. One of such additives may be used
alone, or two or more of them may be used in an optional
combination and ratio.
[4-5. Construction of Light-Emitting Device (Other)]
[0232] So long as the light-emitting device of the present
invention comprises the above first illuminant and second
illuminant, other constructions are not particularly limited.
However, the above first illuminant and second illuminant are
usually disposed on a suitable frame. At that time, the second
illuminant is excited by the emission of the first illuminant (i.e.
the first and second phosphors are excited) to emit light, and the
arrangement is made so that the emission of this first illuminant
and/or the emission of the second illuminant is taken out. In such
a case, the first phosphor and the second phosphor may not
necessarily be mixed in the same layer, and for example, phosphors
may be contained in separate layers for the respective emission
colors of the phosphors, for example, such that a layer containing
the second phosphor is laminated on a layer containing the first
phosphor.
[0233] In the light-emitting device of the present invention, in
addition to the above excitation light source (the first
illuminant), the phosphor (the second phosphor) and the frame,
another component may be used. As such an example, the
above-mentioned sealing material may be mentioned. In addition to
the purpose of dispersing the phosphor (the second illuminant) in
the light-emitting device, such a sealing material may be used for
the purpose of bonding the excitation light source (the first
illuminant), the phosphor (the second illuminant) and the
frame.
[4-6. Embodiments of Light-Emitting Device]
[0234] Now, the light-emitting device of the present invention will
be described in further detail with reference to a specific
embodiment, but it should be understood that the light-emitting
device of the present invention is by no means restricted to the
following embodiment, and it may be practiced by modifying it
optionally within a range not to depart from the gist of the
present invention.
[0235] FIG. 1 shows a diagrammatical perspective view illustrating
the positional relation between the first illuminant to be an
excitation light source and the second illuminant constructed as a
phosphor-containing portion having the phosphor, in one embodiment
of the light-emitting device of the present invention. In FIG. 1,
reference numeral 1 represents a phosphor-containing portion (the
second illuminant), reference numeral 2 represents a
surface-emitting GaN type LD as an excitation light source (the
first illuminant), and reference numeral 3 represents a substrate.
In order to make a mutually contracted state, LD(2) and the
phosphor-containing portion (the second illuminant) (1) may be
prepared separately, and their surfaces may be bonded to each other
by an adhesive or other means, or on the light-emitting surface of
LD(2), the phosphor-containing portion (the second illuminant) may
be formed as a film. Consequently, LD(2) and the
phosphor-containing portion (the second illuminant) (1) can be made
to be in contact with each other.
[0236] By adopting such a construction of the device, it is
possible to avoid a loss of light quantity such that light from the
excitation light source (the first illuminant) is reflected at the
film surface of the phosphor-containing portion (the second
illuminant) and discharged outside, whereby the luminous efficiency
of the entire device can be made good.
[0237] FIG. 2(a) is a diagrammatical cross-sectional view
illustrating an embodiment of the light-emitting device having an
excitation light source (the first illuminant) and a
phosphor-containing portion (the second illuminant), which is a
typical example of a light-emitting device in the form which is
commonly called a shell form. In the light-emitting device (4),
reference numeral 5 represents a mount lead, reference numeral 6 an
inner lead, reference numeral 7 an excitation light source (the
first illuminant), reference numeral 8 a phosphor-containing resin
portion, reference numeral 9 a conductive wire, and reference
numeral 10 a molded component.
[0238] FIG. 2(b) is a diagrammatical cross-sectional view
illustrating one embodiment of the light-emitting device having an
excitation light source (the first illuminant) and a
phosphor-containing portion (the second illuminant), which is a
typical example of a light-emitting device in the form which is
called a surface-mounting type. In the Fig., reference numeral 22
represents an excitation light source (the first illuminant),
reference numeral 23 a phosphor-containing resin portion as the
phosphor-containing portion (the second illuminant), reference
numeral 24 a frame, reference numeral 25 a conductive wire, and
reference numerals 26 and 27 electrodes.
[4-7. Uses of Light-Emitting Device]
[0239] Uses of the light-emitting device of the present invention
are not particularly limited, and it is useful in various fields
wherein usual light-emitting devices are employed. However, it is
particularly suitably employed as a light source for a lighting
system or an image display device, since its color reproduction
range is wide and the color rendering properties are high.
[5. Lighting System]
[0240] The lighting system of the present invention is one provided
with the light-emitting device of the present invention. In a case
where the light-emitting device of the present invention is applied
to the lighting system, the above-described light-emitting device
may be suitably incorporated to a known lighting system. For
example, as shown in FIG. 3, a surface-emitting lighting system
(11) may be mentioned wherein the above-described light-emitting
device (4) is incorporated.
[0241] FIG. 3 is a diagrammatical cross-sectional view illustrating
an embodiment of the lighting system of the present invention. As
shown in this FIG. 3, the surface-emitting lighting system is such
that on the bottom surface of a rectangular casing (12) having the
inner surface made opaque with e.g. a white smooth surface, many
light-emitting devices (13) (corresponding to the above-described
light-emitting device (4)) are disposed, while a light source, a
circuit, etc. (not shown) to drive the light-emitting devices (13)
are provided outside the light-emitting devices, and to make the
emission uniform, a diffuse panel (14) made of e.g. a milky white
acrylic plate, is fixed at the portion corresponding to a cover of
the casing (12).
[0242] And, by driving the surface-emitting lighting system (11) to
apply a voltage to the excitation light source (the first
illuminant) of the light-emitting devices (13) to have light
emitted, and a part of the emitted light is absorbed by the
phosphor in the phosphor-containing resin portion as the
phosphor-containing portion (the second illuminant) to have a
visible light emitted, while by color mixing with blue light, etc.
not absorbed by the phosphor, an emission having high color
rendering properties can be obtained, and this light is transmitted
through the diffuser panel (14) and emitted upwards in the drawing,
whereby illumination light having a uniform brightness will be
obtained in the plane of the diffuser panel (14) of the casing
(12).
[6. Image Display Device]
[0243] The image display device of the present invention is one
provided with the light-emitting device of the present invention.
In a case where the light-emitting device of the present invention
is used as a light source for an image display device, there is no
particularly limitation to the specific construction of the image
display device, but it is preferably used together with a color
filter. For example, in a case where the image display device is a
color image display device utilizing a color liquid crystal display
element, it is possible to form an image display device by using
the above-described light-emitting device as a backlight and
combining an optical shutter utilizing liquid crystal with color
filters having red, green and blue pixels.
[0244] The color reproduction range by light after passing through
the color filters at that time, is, by NTSC ratio, usually at least
60%, preferably at least 80%, more preferably at least 90%, further
preferably at least 100%, and usually at most 150%. Further, the
amount of transmitted light from each color filter (light use
efficiency) to the amount of transmitted light from the entire
color filters is usually at least 20%, preferably at least 25%,
more preferably at least 28%, further preferably at least 30%. The
light use efficiency should better be high, but as three filters of
red, green and blue are used, it is usually at most 33%.
EXAMPLES
[0245] Now, the present invention will be described in further
detail with reference to Examples and Comparative Examples, but it
should be understood that the present invention is by no means
restricted to the following Examples, and may be practiced by
making optional changes within a range not to depart from the gist
of the present invention. Here, measurement of emission properties,
etc. of phosphors in Examples and Comparative Examples were carried
out by the following methods.
[Measuring Methods]
[0246] [Emission Spectrum]
[0247] The emission spectrum was measured by means of a
fluorescence measuring apparatus (manufactured by JASCO
Corporation) provided with a 150 W xenon lamp as an excitation
light source and a multichannel CCD detector C7041 (manufactured by
Hamamatsu Photonics) as a spectrum-measuring device. Light from the
excitation light source was passed through a diffraction grating
spectroscope having a focal distance of 10 cm, and only excitation
light having a wavelength of 460 nm was radiated to the phosphor
via an optical fiber. Light generated from the phosphor under
irradiation with the excitation light was spectrally divided by a
diffraction grating spectroscope having a focal distance of 25 cm,
whereby emission intensities at various wavelengths were measured
by the spectrum measuring apparatus within the wavelength range of
from 300 nm to 800 nm, and via signal treatments such as
sensitivity correction by a personal computer, an emission spectrum
was obtained. Here, at the time of the measurement, the measurement
was carried out by setting the slit width of the light-receiving
side spectroscope to be 1 nm.
[Chromaticity Coordinates]
[0248] The chromaticity coordinates of x, y color system (CIE 1931
color system) were calculated as chromaticity coordinates x and y
in the XYZ color system as stipulated in JIS Z8701 by a method in
accordance with JIS 28724 from the data in the wavelength region of
from 420 nm to 800 nm of the emission spectrum obtained by the
above-described method.
[Absorption Efficiency]
[0249] The absorption efficiency .alpha..sub.q of a phosphor was
obtained as follows. Firstly, a phosphor sample to be measured was
made to have its surface sufficiently smooth so that the
measurement accuracy was maintained and packed into a cell, which
was attached to an integrating sphere.
[0250] To this integrating sphere, light was introduced by means of
an optical fiber from an emission light source (150 W Xe lamp) to
excite the phosphor. The emission peak wavelength of light from the
above emission light source was adjusted by means of e.g. a
monochrometer (diffraction grating spectroscope) to be a
monochromatic light of 455 nm. Such a monochromatic light was
radiated as an excitation light to the phosphor sample to be
measured, and by means of a spectroscopic apparatus (MCPD7000
manufactured by Otsuka Electronics Co., Ltd.), the emission
(fluorescence) of the phosphor sample and the spectrum with respect
to the reflected light, were measured. The light in the integrating
sphere was led to a spectroscopic apparatus by means of an optical
fiber.
[0251] The absorption efficiency .alpha..sub.q is a value obtained
by dividing the photon number N.sub.abs of the excitation light
absorbed by the phosphor sample, by the total photon number N of
the excitation light.
[0252] The latter total photon number N of the excitation light is
proportional to the numerical value obtained by the following
formula (Formula a). Therefore, as a reflector having a reflectance
R of substantially 100% to the excitation light, "Spectralon"
manufactured by Labsphere (having a reflectance R of 98.8% to a
light source of 455 nm) was attached, as an object to be measured,
to the above-mentioned integrating sphere in the same disposition
as the phosphor sample and irradiated with an excitation light,
whereby the reflection spectrum I.sub.ref(.lamda.) was measured by
a spectroscopic apparatus, and the value of the following formula
(Formula a) was obtained.
1 R .intg. .lamda. I ref ( .lamda. ) .lamda. Formula a
##EQU00001##
[0253] Here, the integral interval was set to be from 410 nm to 480
nm to an excitation wavelength of 455 nm. The photon number
N.sub.abs of the excitation light absorbed by the phosphor sample
is proportional to the amount obtained by the following formula
(Formula b).
1 R .intg. .lamda. I ref ( .lamda. ) .lamda. - .intg. .lamda. I (
.lamda. ) .lamda. Formula b ##EQU00002##
[0254] Therefore, the reflection spectrum I (.lamda.) was obtained
when the reflection sample as the object to obtain the absorption
efficiency .alpha..sub.q was attached. The integration range of the
Formula b was set to be the same as the integration range set for
the Formula a. The actual measured value of spectrum is usually
obtained as digital data divided into finite band widths relating
to .lamda., and accordingly, the integrations of the Formula a and
the Formula b were obtained by summation based on the band widths.
Thus, .alpha..sub.q=N.sub.abx/N=(Formula b)/(Formula a) was
calculated. Here, the reflectance was obtained by using light with
a wavelength of 780 nm whereby in the phosphor, substantially no
absorption or emission takes place.
[Object Color]
[0255] The measurement of the object color was carried out by means
of color difference meter CR300 manufactured MINOLTA using D65 as
the standard light. A sample was packed in a circular cell and its
surface was flattened, and the measurement was carried out by
pressing the flattened surface to the measuring portion of the
color difference meter.
[Carbon Content, Oxygen Content]
[0256] A sample was put in an impulse furnace, and oxygen and
carbon were extracted by heating, whereupon the oxygen content
concentration and the carbon content concentration were determined
by nondispersive infrared detection.
[SEM-EDX]
[0257] The elemental composition of apart of phosphor particles,
e.g. the composition of Gd, Y, etc., was analyzed by SEM-EDX
(Scanning Electron Microscope-Energy Dispersive X-ray spectrometer)
(S-3400N manufactured by Hitachi, Ltd.)
Example 1
Production of Alloy
[0258] Respective metal raw materials of Ca solid metal blank, La
solid metal blank, Ce solid metal blank and Si solid metal blank,
were weighed so that the compositional ratio of metal elements
would be Ca:La:Ce:Si=0.45:2.5:0.1:6 (molar ratio) and melted by a
high frequency meting furnaces to obtain an alloy. Then, the alloy
was pulverized by a jet mill to obtain an alloy powder a having a
median diameter of 4.3 .mu.m.
Firing of Raw Material
[0259] In a glove box containing nitrogen as an operation
atmosphere, 1 g of the alloy powder, 0.06 g of MgF.sub.2 (6 wt % to
the alloy material) and 0.08 g of CeF.sub.3 (8 wt % to the alloy
material) were mixed in an alumina mortar, and the mixture was
spread on a molybdenum tray having a diameter of 30 mm and set in
an electric furnace with a molybdenum inner wall having a tungsten
heater. After vacuuming from room temperature to 120.degree. C., 4%
hydrogen-containing nitrogen gas was introduced to ordinary
pressure, and while maintaining the supply rate of 0.5 L/min, the
temperature was raised to 800.degree. C. and then raised from 800
to 1,550.degree. C. at a rate of 0.5.degree. C./min, followed by
firing at 1,550.degree. C. for 15 hours, whereupon the fired
product was pulverized in an alumina mortar.
Treatment of Fired Product
[0260] The obtained fired product was pulverized in an agate
mortar, and the obtained powder was stirred and cleaned with a
NH.sub.4HF.sub.2 aqueous solution having a concentration of 10 wt %
for 1 hour, followed by washing with water and drying to obtain a
phosphor. The firing conditions, etc. of this phosphor and the
results of property evaluations (the emission properties,
absorption efficiency and object color) are shown in Table 1. Here,
in Table 1, the luminance (%) and the emission intensity (%) are
relative values to a YAG commercial product (P46-Y3 manufactured by
Kasei Optonix) being 100%. The phosphor in Example 1 had a
luminance as high as 119% to P46-Y3; a* and b* representing the
object color were -14 and 88, respectively; the chroma
(a*.sup.2+b*.sup.2).sup.1/2 was very high at 89; and the absorption
efficiency was very high at 92%.
Example 2
[0261] A phosphor was obtained in the same manner as in Example 1
except that the cleaning with the ammonium hydrogen fluoride
(NH.sub.4HF.sub.2) aqueous solution was not carried out, and
evaluations of its properties were carried out. The firing
conditions, etc. of this phosphor and the evaluation results of the
properties are shown in Table 1. The phosphor in Example 2 had a
luminance of 106% to P46-Y3; a* and b* representing the object
color were -11 and 83, respectively; the chroma
(a*.sup.2+b*.sup.2).sup.1/2 was 84; and the absorption efficiency
was 92%. When Example 2 is compared with Example 1, the absorption
efficiency was equal, but Example 1 was superior with respect to
other values, thus indicating that the effects of cleaning with the
NH.sub.4HF.sub.2 aqueous solution are distinct.
Example 3
[0262] A phosphor was obtained in the same manner as in Example 1
except that the amount of CeF.sub.3 added was 6 wt %, and
evaluations of its properties were carried out. The firing
conditions, etc. of this phosphor and the evaluation results of the
properties are shown in Table 1.
[0263] The content concentration of carbon in the phosphor obtained
in Example 3 was 0.03 wt %. The carbon content concentration in the
raw material alloy of this phosphor was 0.3 wt %, and the oxygen
content concentration was 0.6 wt %. This indicates that by the
firing in 4% hydrogen-containing nitrogen gas, the carbon content
in the phosphor was reduced to 0.03 wt %. That is, it is evident
that in this Example, the firing in the hydrogen-containing
nitrogen atmosphere finally contributed to reduction of the amount
of carbon in the phosphor, and as a result, an extremely high
luminance was obtained. Thus, according to the method of the
present invention, it is possible to obtain a phosphor having high
luminance by using an alloy produced by using a graphite crucible.
This sample in Example 3 was further subjected to cleaning with 1N
hydrochloric acid, and then, the same chemical analysis as in
Example A1 was carried out, whereby the chemical formula of the
phosphor obtained was found to be
Ca.sub.0.04La.sub.2.7Ce.sub.0.30Si.sub.6O.sub.11O.sub.0.26.
Example 4
[0264] A phosphor was obtained in the same manner as in Example 3
except that the cleaning with the NH.sub.4HF.sub.2 aqueous solution
was not carried out, and evaluations of its properties were carried
out. The firing conditions, etc. of this phosphor and the
evaluation results of the properties are shown in Table 1. When
Example 3 and Example 4 are compared, it is evident that the
effects for improving the luminance and emission intensity, of the
cleaning with the NH.sub.4HF.sub.2 aqueous solution, are
distinct.
Example 5
[0265] A phosphor was obtained in the same manner as in Example 1
except that the amount of CeF.sub.3 was changed to 4 wt %, and
evaluations of its properties were carried out. The firing
conditions, etc. of this phosphor and the evaluation results of the
properties are shown in Table 1.
Example 6
[0266] A phosphor was obtained in the same manner as in Example 5
except that the cleaning with the NH.sub.4HF.sub.2 aqueous solution
was not carried out, and evaluations of its properties were carried
out. The firing conditions, etc. of this phosphor and the
evaluation results of the properties are shown in Table 1. When
Example 5 and Example 6 are compared, it is evident that by the
cleaning with the NH.sub.4HF.sub.2 aqueous solution, the luminance
and the absorption efficiency are improved.
Example 7
[0267] A phosphor was obtained in the same manner as in Example 1
except that the amount of CeF.sub.3 was changed to 2 wt %, and
evaluations of its properties were carried out. The firing
conditions, etc. of this phosphor and the evaluation results of the
properties are shown in Table 1.
Example 8
[0268] A phosphor was obtained in the same manner as in Example 7
except that the cleaning with the NH.sub.4HF.sub.2 aqueous solution
was not carried out, and evaluations of its properties were carried
out. The firing conditions, etc. of this phosphor and the
evaluation results of the properties are shown in Table 1. When
Example 7 and Example 8 are compared, it is evident that the
effects for improving the luminance and emission intensity, of the
cleaning with the NH.sub.4HF.sub.2 aqueous solution, are
distinct.
Example 9
[0269] A phosphor was obtained in the same manner as in Example 1
except that 6% of only MgF.sub.2 was added, and CeF.sub.3 was not
added, and evaluations of its properties were carried out. The
firing conditions, etc. of this phosphor and the evaluation results
of the properties are shown in Table 1.
Comparative Example 1
[0270] A phosphor was obtained in the same manner as in Example 9
except that the cleaning with the NH.sub.4HF.sub.2 aqueous solution
was not carried out, and evaluations of its properties were carried
out. The firing conditions, etc. of this phosphor and the
evaluation results of the properties are shown in Table 1. When
Example 9 and Comparative Example 1 are compared, it is evident
that by the cleaning with the NH.sub.4HF.sub.2 aqueous solution,
the luminance, emission intensity and object color are
improved.
Example 10
[0271] A phosphor was obtained in the same manner as in Example 1
except MgF.sub.2 was 6%, CeF.sub.3 was 6%, LaF.sub.3 was 2%, and
the heating retention time was 40 hours, and evaluations of its
properties were carried out. The firing conditions, etc. of this
phosphor and the evaluation results of the properties are shown in
Table 1. The phosphor in Example 10 had a luminance of 118% to
P46-Y3; a* and b* representing the object color were -13 and 89,
respectively; the chroma (a*.sup.2+b*.sup.2).sup.1/2 was high at
90; and the absorption efficiency showed a high value of 93%.
Example 11
[0272] A phosphor was obtained in the same manner as in Example 10
except that the cleaning with the NH.sub.4HF.sub.2 aqueous solution
was not carried out, and evaluations of its properties were carried
out. The firing conditions, etc. of this phosphor and the
evaluation results of the properties are shown in Table 1. The
phosphor in Example 11 had a luminance as high as 97% to P46-Y3; a*
and b* representing the object color were -10 and 79, respectively;
the chroma (a*.sup.2+b*.sup.2).sup.1/2 was high at 80; and the
absorption efficiency showed a high value of 94%. When Example 11
is compared with Example 10, the absorption efficiency is
substantially equal, but Example 10 is superior with respect to
other values, whereby it is evident that the effects of cleaning
with the NH.sub.4HF.sub.2 aqueous solution are distinct.
Example 12
[0273] A phosphor was obtained in the same manner as in Example 10
except that the type and blend amount of the flux were as shown in
Table 1, and evaluations of its properties were carried out. The
firing conditions, etc. of this phosphor and the evaluation results
of the properties are shown in Table 1.
Example 13
[0274] A phosphor was obtained in the same manner as in Example 12
except that the cleaning with the NH.sub.4HF.sub.2 aqueous solution
was not carried out, and evaluations of its properties were carried
out. The firing conditions, etc. of this phosphor and the
evaluation results of the properties are shown in Table 1. When
Example 12 and Example 13 are compared, it is evident that the
effects for improving the luminance, of the cleaning with the
NH.sub.4HF.sub.2 aqueous solution, are distinct.
Example 14
[0275] A phosphor was obtained in the same manner as in Example 10
except that the type and blend amount of the flux were as shown in
Table 1, and evaluations of its properties were carried out. The
firing conditions, etc. of this phosphor and the evaluation results
of the properties are shown in Table 1.
Example 15
[0276] A phosphor was obtained in the same manner as in Example 14
except that the cleaning with the NH.sub.4HF.sub.2 aqueous solution
was not carried out, and evaluations of its properties were carried
out. The firing conditions, etc. of this phosphor and the
evaluation results of the properties are shown in Table 1. When
Example 14 and Example 15 are compared, it is evident that the
effects for improving the luminance, of the cleaning with the
NH.sub.4HF.sub.2 aqueous solution, are distinct.
Example 16
[0277] A phosphor was obtained in the same manner as in Example 10
except that the type and blend amount of the flux were as shown in
Table 1, and evaluations of its properties were carried out. The
firing conditions, etc. of this phosphor and the evaluation results
of the properties are shown in Table 1.
Example 17
[0278] A phosphor was obtained in the same manner as in Example 16
except that the cleaning with the NH.sub.4HF.sub.2 aqueous solution
was not carried out, and evaluations of its properties were carried
out. The firing conditions, etc. of this phosphor and the
evaluation results of the properties are shown in Table 1. When
Example 16 and Example 17 are compared, it is evident that by the
cleaning with the NH.sub.4HF.sub.2 aqueous solution, the luminance
and object color are improved.
Example 18
[0279] A phosphor was obtained in the same manner as in Example 16
except CeF.sub.3 was not added, and evaluations of its properties
were carried out. The firing conditions, etc. of this phosphor and
the evaluation results of the properties are shown in Table 1.
Comparative Example 2
[0280] A phosphor was obtained in the same manner as in Example 18
except that the cleaning with the NH.sub.4HF.sub.2 aqueous solution
was not carried out, and evaluations of its properties were carried
out. The firing conditions, etc. of this phosphor and the
evaluation results of the properties are shown in Table 1. When
Example 18 and Comparative Example 2 are compared, it is evident
that by the cleaning with the NH.sub.4HF.sub.2 aqueous solution,
the luminance, absorption efficiency and object color are
improved.
TABLE-US-00001 TABLE 1 Ex. or Firing conditions Comp. First flux
Second flux Third flux Firing Ex. Amount Amount Amount time
Cleaning No. Type (%) Type (%) Type (%) (hr) with acid Ex. 1
MgF.sub.2 6 CeF.sub.3 8 -- -- 15 Yes Ex. 2 MgF.sub.2 6 CeF.sub.3 8
-- -- 15 No Ex. 3 MgF.sub.2 6 CeF.sub.3 6 -- -- 15 Yes Ex. 4
MgF.sub.2 6 CeF.sub.3 6 -- -- 15 No Ex. 5 MgF.sub.2 6 CeF.sub.3 4
-- -- 15 Yes Ex. 6 MgF.sub.2 6 CeF.sub.3 4 -- -- 15 No Ex. 7
MgF.sub.2 6 CeF.sub.3 2 -- -- 15 Yes Ex. 8 MgF.sub.2 6 CeF.sub.3 2
-- -- 15 No Ex. 9 MgF.sub.2 6 CeF.sub.3 0 -- -- 15 Yes Comp.
MgF.sub.2 6 CeF.sub.3 0 -- -- 15 No Ex. 1 Ex. 10 MgF.sub.2 6
CeF.sub.3 6 LaF.sub.3 2 40 Yes Ex. 11 MgF.sub.2 6 CeF.sub.3 6
LaF.sub.3 2 40 No Ex. 12 MgF.sub.2 6 CeF.sub.3 8 -- -- 40 Yes Ex.
13 MgF.sub.2 6 CeF.sub.3 8 -- -- 40 No Ex. 14 MgF.sub.2 6 CeF.sub.3
10 -- -- 40 Yes Ex. 15 MgF.sub.2 6 CeF.sub.3 10 -- -- 40 No Ex. 16
MgF.sub.2 6 CeF.sub.3 6 -- -- 40 Yes Ex. 17 MgF.sub.2 6 CeF.sub.3 6
-- -- 40 No Ex. 18 MgF.sub.2 6 CeF.sub.3 0 -- -- 40 Yes Comp.
MgF.sub.2 6 CeF.sub.3 0 -- -- 40 No Ex. 2 Ex. or Evaluation results
of properties Comp. Emission properties (455 nm excitation)
Absorption Object color Ex. Emission peak Chromaticity Chromaticity
Luminance Emission efficiency Luminosity Chroma No. wavelength (nm)
coordinate x coordinate y (%) intensity (%) (%) L* a* b* (a*.sup.2
+ b*.sup.2).sup.0.5 Ex. 1 540 0.441 0.539 119 119 92 96 -14 88 89
Ex. 2 542 0.444 0.537 106 107 92 92 -11 83 84 Ex. 3 540 0.440 0.540
115 115 -- -- -- -- -- Ex. 4 540 0.441 0.539 101 103 -- -- -- -- --
Ex. 5 542 0.442 0.539 117 117 92 -- -- -- -- Ex. 6 542 0.440 0.540
102 105 88 -- -- -- -- Ex. 7 540 0.441 0.539 117 117 -- -- -- -- --
Ex. 8 540 0.440 0.540 99 101 -- -- -- -- -- Ex. 9 540 0.430 0.545
105 105 84 95 -16 75 76 Comp. 537 0.429 0.545 94 96 84 94 -14 64 66
Ex. 1 Ex. 10 540 0.438 0.542 118 120 93 95 -13 89 90 Ex. 11 539
0.439 0.541 97 98 94 86 -10 79 80 Ex. 12 540 0.441 0.540 117 120 92
-- -- -- -- Ex. 13 538 0.442 0.539 98 100 94 -- -- -- -- Ex. 14 541
0.441 0.540 116 117 94 -- -- -- -- Ex. 15 542 0.444 0.538 97 98 93
-- -- -- -- Ex. 16 541 0.440 0.541 113 115 94 95 -13 90 91 Ex. 17
540 0.440 0.540 94 95 93 86 -10 78 79 Ex. 18 537 0.426 0.549 108
110 92 93 -16 79 81 Comp. 534 0.426 0.548 85 86 88 88 -12 65 66 Ex.
2 Notes) -- : Nil or not measured. Washing with acid: After the
firing, washing for 1 hour with a 10% NH.sub.4HF.sub.2 aqueous
solution. Luminance (%): Relative value to luminance of YAG
commercial product (P46-Y3) being 100%. Emission intensity (%):
Relative value to emission intensity of YAG commercial product
(P46-Y3) being 100%.
Comparative Example 3
[0281] CaSiN.sub.2, LaN, CeO.sub.2 and Si.sub.3N.sub.4
(manufactured by Denki Kagaku Kogyo Kabushiki Kaisha, average
particle diameter: 0.5 .mu.m, oxygen content: 0.93 wt %,
.alpha.-type content: 92%) were weighed as raw materials, and in a
crucible made of boron nitride, 1.7 g of the raw material mixture
was fired at 2,000.degree. C. under a nitrogen pressure of 0.92 MPa
to obtain a phosphor. Here, the charged amounts of the respective
raw materials, the firing conditions, etc. are the same as in
Example 8 in JP-A-2008-285659. The charged amounts and the firing
conditions, etc. are shown in Table 2. Further, the evaluation
results of the properties of the obtained phosphor (emission
properties, absorption efficiency and object color) are shown in
Table 3.
TABLE-US-00002 TABLE 2 Charged amounts of the respective Charged
amount Firing Comp. raw materials (g) (molar ratio) temp. Ex. No.
CaSiN.sub.2 LaN CeO.sub.2 Si.sub.3N.sub.4 Ca La Ce (.degree. C.)
Comp. 0.546 0.642 0.044 0.467 2.2 1.6 0.10 2000 Ex. 3 Note) Charged
amounts (molar ratio): Molar ratio of each element to 6 mol of Si
charged.
TABLE-US-00003 TABLE 3 Emission properties (460 nm excitation)
Emission Emission peak Absorption Object color Comp. Ex. intensity
wavelength Chromaticity Chromaticity efficiency Luminosity Chroma
No. (%) (nm) coordinate x coordinate y (%) L* a* b* (a*.sup.2 +
b*.sup.2).sup.0.5 Comp. 49 591 0.519 0.473 85 85 8 59 59 Ex. 3
Note) Emission intensity (%): Relative value to luminance of YAG
commercial product (P46-Y3) being 100%.
[0282] Of the phosphor in Comparative Example 3, a* and b*
representing the object color were 8 and 59, respectively; the
chroma (a*.sup.2+b*.sup.2).sup.1/2 was as low as 59; and the
absorption efficiency showed a relatively low value of 85%. From
such results, it is evident that the phosphors of the present
invention in Examples 1 to 18 have higher luminance than the
phosphor in Comparative Example 3 (Example 8 in JP-A-2008-285659)
and have high chroma and high absorption efficiency and different
values a* and b* for object color.
Comparative Example 4
[0283] CaSiN.sub.2 powder, .alpha.-Si.sub.3N.sub.4 powder, LaN
powder and La.sub.4CeSi.sub.10 alloy powder were mixed in weight
ratios of 0.352, 0.975. 1.574 and 0.468, respectively. About 0.7 g
of the mixture was charged into a crucible made of boron nitride
and fired (primary firing) at 2,000.degree. C. under a nitrogen
pressure of 0.92 MPa, followed by secondary firing in the presence
of MgF.sub.2 flux to obtain a phosphor. The raw materials, charged
amounts, firing conditions, etc. in this Comparative Example 4 are
the same as in Example II-6 in WO2008-132954. The charged raw
materials for the phosphor and the firing conditions, etc. in
Comparative Example 4 are shown in Table 4. Further, the evaluation
results of properties of the obtained phosphor (emission
properties, absorption efficiency and object color) are shown in
Table 5.
Comparative Example 5
[0284] CaSiN.sub.2 powder, .beta.-Si.sub.3N.sub.4 powder, LaN
powder and La.sub.4CeSi.sub.10 alloy powder were mixed in weight
ratios of 0:261, 0.723, 1.168 and 0.347, respectively. About 1.2 g
of the mixture was charged into a crucible made of boron nitride
and fired (primary firing) at 2,000.degree. C. under a nitrogen
pressure of 0.92 MPa, followed by secondary firing in the presence
of MgF.sub.2 flux to obtain a phosphor. The charged raw materials
for the phosphor and the firing conditions, etc. in Comparative
Example 5 are shown in Table 4. Further, the evaluation results of
the properties of the obtained phosphor (emission properties,
absorption efficiency and object color) are shown in Table 5.
TABLE-US-00004 TABLE 4 Primary firing conditions Second firing
conditions Firing Firing Comp. Charged raw Pressure temperature
.times. Pressure temperature .times. Ex. No. materials Atmosphere
(Pa) time Flux Atmosphere (Pa) time Comp. La.sub.4CeSi.sub.10 N2
0.92 1,580.degree. C. .times. 57 hr + MgF.sub.2 N2 0.92
1,580.degree. C. .times. 6 hr Ex. 4 alloy + LaN + .alpha.-
2,000.degree. C. .times. 0.08 hr 0.9 wt % Si.sub.3N.sub.4 +
CaSiN.sub.2 Comp. La.sub.4CeSi.sub.10 N2 0.92 1,580.degree. C.
.times. 57 hr + MgF.sub.2 N2 0.92 1,580.degree. C. .times. 6 hr Ex.
5 alloy + LaN + .beta. 2,000.degree. C. .times. 0.08 hr 0.9 wt %
Si.sub.3N.sub.4 + CaSiN.sub.2
TABLE-US-00005 TABLE 5 Emission properties (460 nm excitation)
Emission Emission peak Absorption Object color Comp. Ex. intensity
wavelength Chromaticity Chromaticity efficiency Luminosity Chroma
No. (%) (nm) coordinate x coordinate y (%) L* a* b* (a*.sup.2 +
b*.sup.2).sup.0.5 Comp. Ex. 4 76 564 0.457 0.520 83 94 -8 62 62
Comp. Ex. 5 78 561 -- -- 87 94 -7 70 71 Note) Emission intensity
(%): Relative value to luminance of YAG commercial product (P46-Y3)
being 100%.
[0285] Of the phosphors in Comparative Examples 4 and 5, a* and b*
representing the object color were -8 and -7, and 62 and 70,
respectively; the chroma (a*.sup.2+b*.sup.2).sup.1/2 was as low as
62 and 71, respectively; and the absorption efficiency showed
relatively low values of 83 and 87%, respectively.
[0286] From such results, it is evident that the phosphors of the
present invention in Examples 1 to 18 have higher luminance than
the phosphor disclosed in Example in WO2008-132954, have high
chroma and high absorption efficiency, and have different values a*
and b* of object color.
Example 19
Low Temperature Raise in Alloy-Nitriding Temperature Region
[0287] A phosphor was obtained by firing under the same conditions
as in Example 9 except that in Example 9, only in the temperature
region of from 1,250 to 1,350.degree. C., the temperature raising
rate was changed from 0.5.degree. C./min to 0.1.degree. C./min. The
evaluation results of the properties of this phosphor (emission
properties, absorption efficiency and object color) are shown in
Table 6. Further, the evaluation results of the phosphor in Example
9 are shown for the purpose of comparison in Table 6.
TABLE-US-00006 TABLE 6 Emission properties (455 nm excitation)
Emission peak Emission Absorption Object color Comp. wavelength
Chromaticity Chromaticity Luminance intensity efficiency Luminosity
Chroma Ex. No. (nm) coordinate x coordinate y (%) (%) (%) L* a* b*
(a*.sup.2 + b*.sup.2).sup.0.5 Ex. 19 540 0.435 0.543 112 114 92 94
-16 87 88 Ex. 9 540 0.430 0.545 105 105 84 95 -16 76 77 Note)
Luminance (%): Relative value to luminance of YAG commercial
product (P46-Y3) being 100%. Emission intensity (%): Relative value
to luminance of YAG commercial product (P46-Y3) being 100%.
[0288] The phosphor in Example 19 had a luminance of 112% to
P46-Y3, which was higher than the luminance of 105% in Example 9.
This temperature range corresponds to the portion of from rising to
termination of the heat generation peak during the nitriding
reaction of the raw material alloy. It was found that by reducing
the temperature raising rate in this temperature range, it is
possible to improve the luminance.
Examples 20 and 21
Alloy Composition
[0289] An experiment was carried out under the same conditions as
in Example 19 except that in Example 19, the flux was changed to 6
wt % of MgF.sub.2, 6 wt % of CeF.sub.3 and 2 wt % of CaF.sub.2
(Example 20). An experiment was carried out under the same
conditions as in Example 20 except that in this Example 20, the
charged raw material was changed to an alloy of
Ca.sub.0.75La.sub.2.6Ce.sub.0.1Si.sub.6 (Example 21). The charged
raw materials for the phosphors (alloy compositions) and the firing
conditions, etc. in Examples 20 and 21 are shown in Table 7.
Further, the evaluation results of properties of the obtained
phosphors (emission properties, absorption efficiency and object
color) are shown in Table 8.
TABLE-US-00007 TABLE 7 Charged raw Firing conditions materials
(alloy First flux Second flux Third flux Ex. No. composition) Type
Amount (%) Type Amount (%) Type Amount (%) Ex. 20
Ca.sub.045La.sub.2.6Ce.sub.0.1Si.sub.6 MgF.sub.2 6 CeF.sub.3 6
LaF.sub.3 2 Ex. 21 Ca.sub.0.75La.sub.2.6Ce.sub.0.1Si.sub.6
MgF.sub.2 6 CeF.sub.3 6 LaF3 2
TABLE-US-00008 TABLE 8 Emission properties (455 nm excitation)
Emission peak Emission Object color Comp. wavelength Chromaticity
Chromaticity Luminance intensity Luminosity Chroma Ex. No. (nm)
coordinate x coordinate y (%) (%) L* a* b* (a*.sup.2 +
b*.sup.2).sup.0.5 Ex. 20 540 0.434 0.543 108 110 97 -15 77 79 Ex.
21 553 0.462 0.524 109 111 94 -7 95 95 Note) Luminance (%):
Relative value to luminance of YAG commercial product (P46-Y3)
being 100%. Emission intensity (%): Relative value to luminance of
YAG commercial product (P46-Y3) being 100%.
[0290] From the results in Examples 20 and 21, it is evident that
when the amount of Ca in the alloy is changed from 0.45 to 0.75,
the high luminance is maintained, while the chromaticity coordinate
value x is remarkably increased.
[0291] The sample in this Example 21 was further subjected to
washing with 1N hydrochloric acid, and then the same chemical
analysis as in Example A1 was carried out, whereby it was found
that the chemical formula of the obtained phosphor, wherein the
amount of Si was 6 mol, was found to be
Ca.sub.0.10La.sub.2.6Ce.sub.0.29Si.sub.6N.sub.11O.sub.0.05. This
substantially agrees to x=0.03, y=0.05, z=0.29 and w1=w2=0.
Examples 22 to 24
Effects of Rare Earth Fluorides
[0292] An experiment was carried out under the same conditions as
in Example 19 except that in Example 19, the flux was changed to 6
wt % of MgF.sub.2 and 6 wt % of CeF.sub.3 (Example 22). An
experiment was carried out under the same conditions as in Example
22 except that in this Example 22, the flux was changed to 6 wt %
of MgF.sub.2, 6 wt % of CeF.sub.3 and 6 wt % of GdF.sub.3 (Example
23). An experiment was carried out under the same conditions as in
Example 22 except that in Example 22, the flux was changed to 6 wt
% of MgF.sub.2, 6 wt % of CeF.sub.3 and 3 wt % of YF.sub.3 (Example
24). The firing conditions for the phosphors in Example 22 to 24
and the evaluation results of properties of the obtained phosphors
(emission properties) are shown in Table 9.
TABLE-US-00009 TABLE 9 Emission properties (455 nm excitation)
Firing conditions Emission First flux Second flux Third flux peak
Amount Amount Amount wavelength Chromaticity Chromaticity Ex. No.
Type (%) Type (%) Type (%) (nm) coordinate x coordinate y Ex. 22
MgF.sub.2 6 CeF.sub.3 6 546 0.445 0.537 Ex. 23 MgF.sub.2 6
CeF.sub.3 6 GdF.sub.3 6 546 0.458 0.527 Ex. 24 MgF.sub.2 6
CeF.sub.3 6 YF.sub.3 3 547 0.452 0.530
[0293] From the results in Examples 22 to 24, it is evident that
YF.sub.3 and GdF.sub.3 have effects to increase the chromaticity
coordinate value x. From the measurements by SEM-EDX, it was found
that Gd and Y were introduced in the crystal particles of such
GdF.sub.3 type phosphor (Example 23) and YF.sub.3 type phosphor
(Example 24). In the crystal particles in Example 23, Gd was found
to have been introduced in an amount of about 0.14 mol to 6 mol of
Si. It is considered that Gd or Y was substituted for La to present
an influence over the crystal field in the vicinity of the Ce
activation element, so that the emission color was changed.
Examples 25 to 30
Types of Flux
[0294] Experiments were carried out in the same manner as in
Example 1 except that in Example 1, the temperature raising rate
from 800.degree. C. was increased to 10''C/min, the firing
temperature was changed to 1,450.degree. C., and the flux was
changed to MgF.sub.2, LIE, NaCl, KCL, BaCl.sub.2 or CaF.sub.2
(Examples 25 to 30). The firing conditions (fluxes) for the
phosphors and the evaluation results of properties of the obtained
phosphors (emission properties) in Examples 25 to 30 are shown in
Table 10.
TABLE-US-00010 TABLE 10 Emission properties Firing (455 nm
excitation) conditions Emission (flux) peak Amount wavelength
Chromaticity Chromaticity Ex No. Type (%) (nm) coordinate x
coordinate y Ex. 25 MgF.sub.2 3 542 0.433 0.536 Ex. 26 LiF 3 546
0.442 0.530 Ex. 27 NaCl 3 556 0.444 0.530 Ex. 28 KCl 3 554 0.446
0.529 Ex. 29 BaCl.sub.2 3 553 0.454 0.525 Ex. 30 CaF.sub.2 10 554
0.443 0.530
[0295] From the results in Example 25 to 30, it is evident that
relative to MgF.sub.2, LiF, NaCl, KCL, BaCl.sub.2 or CaF.sub.2 has
an effect to increase the chromaticity coordinate value x.
Examples 31 to 36
[0296] With respect to phosphors obtained in the same manner as in
Example 1 except that the firing conditions were changed to the
conditions shown in Table 11, the effects of cleaning with an acid
were studied (Examples 31 to 36). The conditions for acid cleaning
and the emission properties of these phosphors are shown in Table
12.
TABLE-US-00011 TABLE 11 Firing conditions Alloy Temp.- raw First
flux Second flux raising Firing Firing material Amount Amount rate
temp. time Ex. No. Amount (g) Type (%) Type (%) (.degree. C.)
(.degree. C.) (hr) Ex. 31 14 MgF.sub.2 6 CeF.sub.3 6 0.1 1550 15
Ex. 32 14 MgF.sub.2 6 CeF.sub.3 6 0.1 1550 15 Ex. 33 14 MgF.sub.2 6
CeF.sub.3 6 0.1 1550 15 Ex. 34 1 MgF.sub.2 6 -- -- 0.5 1500 40 Ex.
35 1 MgF.sub.2 6 -- -- 0.5 1500 40 Ex. 36 1 MgF.sub.2 6 -- -- 0.5
1500 40 Note) Temperature-raising rate: The temperature raising
rate (.degree. C.) in a region of from 1,250 to 1,350.degree.
C.
TABLE-US-00012 TABLE 12-1 Emission properties (455 nm excitation)
Emission Acid cleaning conditions peak Concentration wavelength
Chromaticity Chromaticity Luminance Emission Ex. No. Type of acid
(wt %) Time (hr) (nm) coordinate x coordinate y (%) intensity (%)
Ex. 31 -- -- -- 545 0.443 0.530 100 100 Ex. 32 NH.sub.4HF.sub.2 5 1
546 0.446 0.530 116 116 Ex. 33 NH.sub.4HF.sub.2 10 1 546 0.443
0.531 109 109 Ex. 34 -- -- -- 540 0.433 0.541 100 100 Ex. 35
NH.sub.4HF.sub.2 10 1 541 0.433 0.542 112 116 Ex. 36 HNO.sub.3 35 1
541 0.436 0.541 112 116 Notes) --: Nil. Luminance (%): Relative
value to luminance of a phosphor obtained under the same conditions
without acid washing being 100%. Emission intensity (%): Relative
value to the emission strength of a phosphor obtained under the
same conditions without acid cleaning being 100%.
[0297] From the comparison of Examples 31 and 32, it is evident
that when ammonium hydrogen fluoride (NH.sub.4HF.sub.2) is 5%, the
relative luminance increases by 16% between before and after the
treatment, and from the comparison of Examples 31 and 33, the
relative luminance increases by 9% when the ammonium hydrogen
fluoride is 10%. From the results of Examples 34 to 36, it is
evident that when 35% nitric acid is used instead of 10% ammonium
hydrogen fluoride, the luminance increases by 12% between before
and after the treatment.
Example A1
Production of Alloy
[0298] La metal and Si metal were mixed and melted by an arc
melting method in an argon atmosphere to obtain a LaSi alloy. This
alloy was pulverized by a jet mill to obtain an alloy powder having
a weight median diameter of 7 .mu.m.
Firing of Raw Material
[0299] In a glove box containing nitrogen as the operation
atmosphere, 2.254 g of the alloy powder, 0.631 g of .alpha.-silicon
nitride (SN-E10 manufactured by Ube Industries, Ltd.) and 0.177 g
of CeF.sub.3 were mixed in an alumina mortar, and the mixture was
filled in a molybdenum crucible having a diameter of 20 mm. After
covering with a molybdenum foil, the crucible was set in an
atmosphere firing electric furnace. After vacuuming from room
temperature to 300.degree. C., 4% hydrogen-containing nitrogen gas
was introduced to ordinary pressure, and the temperature was raised
to 1,500.degree. C. and maintained at 1,500.degree. C. for 12
hours, followed by cooling to take out a fired product.
Treatment of Fired Product
[0300] The obtained fired product was pulverized in an alumina
mortar, and the obtained powder was repeatedly stirred with 1 mol/L
hydrochloric acid, cleaned, left to stand still and subjected to
removal of the supernatant, and further left to stand still for 1
day and night, followed by washing with water and drying to obtain
a phosphor.
Evaluations
[0301] The production conditions and the evaluation results of
properties (emission properties, absorption efficiency, object
color, etc.) of this phosphor are shown in Tables 12-5 and 12-6.
Here, the luminance (%) and the emission intensity (%) are
relatively values to a YAG commercial product (P46-Y3 manufactured
by Kasei Optonix) being 100%. The phosphor in Example A1 had a very
high luminance of 137% to P46-Y3; a* and b* representing the object
color were -19.4 and 81.3, respectively; the chroma
(a*.sup.2+b*.sup.2).sup.1/2 was high at 83.5; and the absorption
efficiency was very high at 92%.
[0302] As a result of the compositional analysis of this phosphor,
the contents of La, Ce, Si, N and O were 52.0, 3.74, 22.3, 20.9 and
1.0 wt %, respectively. On this basis, the molar ratio was
calculated based on the total number of moles of La and Ce being 3,
La:Ce:Si:N:O=2.8:0.2:6.0:11:0.47. Here, the contents of La, Ce and
Si were measured by an inductively coupled plasma atomic emission
spectroscopy by using a solution prepared by dissolving the
phosphor treated by alkali fusion treatment. The contents of O and
N were measured by means of an oxygen/nitrogen analyzer TC600
manufactured by LECO. It is considered that since this phosphor was
sufficiently cleaned with hydrochloric acid, a part of the phosphor
was dissolved and converted to an oxide or hydroxide, whereby
oxygen was detected to some extent. Otherwise, the ratio of La, Ce,
Si and N agreed to the composition of a
(La,Ce).sub.3Si.sub.6N.sub.11 crystal.
[0303] The powder X-ray diffraction pattern of this phosphor is
shown in FIG. 4. A pattern was obtained which substantially agreed
to No. 48-1805 of ICDD-JCPDS-PDF data which is a standard pattern
of La.sub.3Si.sub.6N.sub.11.
Examples A2 to A6
[0304] Phosphors were obtained by carrying out the same treatment
as in Example A1 except that the composition of the raw material
was changed as follows.
TABLE-US-00013 TABLE 12-2 LaSi Si.sub.3N.sub.4 CeF.sub.3 YH.sub.3
YF.sub.3 Ex. A2 2.254 0.631 0.177 0.165 0 Ex. A3 2.254 0.631 0.177
0.083 0.131 Ex. A4 2.254 0.631 0.177 0.083 0 Ex. A5 2.254 0.568
0.177 0.083 0.131 Ex. A6 2.254 0.732 0.177 0.083 0.131
[0305] The production conditions and the evaluation results of
properties of the obtained phosphors are shown in Tables 12-5 and
12-6.
[0306] In Example A2, by the addition of YH.sub.3, the emission
wavelength shifted towards a long wavelength side, but the
luminance, etc. were deteriorated.
[0307] In Example A3, the same amount (molar amount) of Y as in
Example A2 was added, but a part of YH.sub.3 was added as YF.sub.3,
whereby the amount of fluorine in the system was increased, and the
crystal growth was promoted, whereby the amount of Y taken into the
phosphor was increased, and the emission wavelength shifted further
to the long wavelength side. At the same time, the crystallinity
became high, and the emission intensity became higher than in
Example A2.
[0308] In Example A4, the amount of YH.sub.3 was made to be a half
as compared with Example A2. The chromaticity coordinate x and the
luminance became intermediate values between Examples A1 and
A2.
[0309] Example A5 represents a phosphor obtained by the same
procedure as in Example A3 except that the amount of
Si.sub.3N.sub.4 added was reduced. By the reduction of silicon
nitride, the luminance and chroma decreased substantially, and the
reason is considered to be an increase of byproducts which hinder
the emission.
[0310] Example A6 represents a phosphor obtained by the same
procedure as in Example A3 except that the amount of
Si.sub.3N.sub.4 added was increased. By the increase of silicon
nitride, the luminance and chroma were improved, and the reason is
considered to be a reduction of byproducts which hinder the
emission, contrary to Example A5.
Example A7
[0311] La metal and Si metal were mixed and melted by means of an
arc melting method in an argon atmosphere to obtain a LaSi alloy.
In a glove box containing nitrogen as an operation atmosphere, this
alloy was pulverized in an alumina mortar and passed through a
nylon mesh having an aperture of 25 .mu.m.
[0312] In a glove box containing nitrogen as an operation
atmosphere, 7.032 g of such an alloy powder, 1.97 g of
.alpha.-silicon nitride (SN-E10 manufactured by Ube Industries,
Ltd.) and 0.541 g of CeF.sub.3 were mixed in an alumina mortar, and
3.1 g of this mixture was sampled and filled in a molybdenum
crucible having a diameter of 20 mm. After covering with a
molybdenum foil, the crucible was set in an atmosphere firing
electric furnace. After vacuuming from room temperature to
300.degree. C., 4% hydrogen-containing nitrogen gas was introduced
to ordinary pressure, and the temperature was raised to
1,500.degree. C. and maintained at 1,500.degree. C. for 12 hours,
followed by cooling to take out a fired product.
[0313] The obtained fired product was pulverized in an alumina
mortar, and the obtained powder was stirred and cleaned with 1
mol/L hydrochloric acid, followed by washing with water and drying
to obtain a phosphor.
[0314] The production conditions and the evaluation results of
properties (emission properties, absorption efficiency, object
color, etc.) of this phosphor are shown in Tables 12-5 and 12-6.
This Example is one carried out substantially in the same procedure
as in Example A1, but the pulverization method of the alloy is
different, whereby the property values such as the luminance and
chroma were different to some extent from those in Example A1.
[0315] As a result of the compositional analysis of this phosphor,
the contents of La, Ce, Si, N and O were 53.0, 3.69, 22.3, 21.0 and
0.2 wt %, respectively. On this basis, the to molar ratios were
calculated based on the total number of moles of La and Ce being 3,
whereby La:Ce:Si:N:O=2.8:0.2:5.9:11:0.08.
[0316] Here, the quantitative measurement was carried out in the
same method as carried out for the phosphor in Example A1. Thus,
the results of measurement which substantially agree to the desired
composition of the (La,Ce).sub.3Si.sub.6N.sub.11 phosphor, were
obtained. The powder X-ray diffraction pattern of this phosphor is
shown in FIG. 5. A pattern which substantially agrees to No.
48-1805 of ICDD-JCPDS-PDF data being a standard pattern of
La.sub.3Si.sub.6N.sub.11, was obtained.
Example A8
[0317] La metal and Si metal were mixed and melted by means of an
arc melting method in an argon atmosphere to obtain a LaSi alloy.
This alloy was pulverized by a jet mill to obtain an ally powder
having a weight median diameter of 10 .mu.m. The raw materials were
weighed in the following weight ratio and mixed in an alumina
mortar.
[0318] LaSi alloy=2.344 g, Si.sub.3N.sub.4=0.656 g, and
CeF.sub.3=0.18 g
[0319] The subsequent procedure was the same as in Example A1, and
a phosphor was produced. The production conditions and the
evaluation results of properties of the obtained phosphor are shown
in Tables 12-5 and 12-6. This phosphor was not subjected to
cleaning treatment, and therefore, the luminance and chroma were
inferior as compared with the phosphor subjected to cleaning
treatment with hydrochloric acid (the following Example A9).
Example A9
[0320] The phosphor in Example A8 was put in 1 mol/L hydrochloric
acid and stirred. It was washed with water and dried to obtain a
phosphor. The production conditions and the evaluation results of
properties of the obtained phosphor are shown in Tables 12-5 and
12-6. The luminance of the phosphor in this Example was
substantially the same as in Example A1, and the chroma of the
phosphor in this Example was higher than the phosphor in Example
A1.
Example A10
[0321] La metal and Si metal were mixed and dissolved by means of a
high frequency melting method in a water-cooled copper crucible in
an argon atmosphere to obtain a LaSi alloy. This alloy was
pulverized by a jet mill to obtain an alloy powder having a weight
median diameter of 11 .mu.m. The raw materials were weighed in the
following weight ratio and mixed in an alumina mortar.
[0322] Using the mixture, a phosphor was produced by the same
procedure as in Examples A8 and A9. The production conditions and
the evaluation results of properties of the obtained phosphor are
shown in Tables 12-5 and 12-6.
Example A11
[0323] The respective metal raw materials were mixed so that the
ratio of La, Ce, Y and Si became 0.42:0.03:0.05:0.5 and melted by
means of an arc melting method in an argon atmosphere to obtain a
(La,Ce,Y)Si alloy. This alloy was pulverized in an alumina mortar
in a glove box with a nitrogen atmosphere and passed through a
nylon mesh having an aperture of 37 .mu.m.
[0324] Using this alloy, a phosphor was obtained by carrying out
the same procedure as in Example A1 except that the blend raw
materials and weight ratio were changed as follows.
[0325] (La,Ce,Y)Si alloy=2.328 g, Si.sub.3N.sub.4=0.672 g, and
LaF.sub.3=0.18 g
[0326] The production conditions and the evaluation results of
properties of the obtained phosphor are shown in Tables 12-5 and
12-6.
Example A12
[0327] The respective raw materials were mixed so that the ratio of
La, Ce, Y and Si became 0.42:0.03:0.05:0.5 and dissolved by means
of a high frequency melting method in a water-cooled copper
crucible in an argon atmosphere to obtain a (La,Ce,Y)Si alloy. This
alloy was pulverized by a jet mill to obtain an alloy powder having
a weight median diameter of 12 .mu.m.
[0328] Using this alloy, a phosphor was obtained by carrying out
the same procedure as in Example A1 except that the blend raw
materials and weight ratio were changed as follows.
[0329] (La,Ce,Y)Si alloy=2.390 g, Si.sub.3N.sub.4=0.610 g, and
LaF.sub.3=0.18 g
[0330] The production conditions and the evaluation results of
properties of the obtained phosphor are shown in Tables 12-5 and
12-6.
Example A13
[0331] La metal, Ce metal and Si metal were mixed so that the ratio
of La:Ce:Si became 2.9:0.1:3.0 and melted by means of an arc
melting method in an argon atmosphere to obtain a LaSi alloy. This
alloy was pulverized by an alumina mortar in a glove box with a
nitrogen atmosphere and passed through a nylon mesh having an
aperture of 25 .mu.m.
[0332] In a glove box containing nitrogen as an operation
atmosphere, 2.345 g of such an alloy powder, 0.656 g of
.alpha.-silicon nitride (SN-E10 manufactured by Ube Industries,
Ltd.) and 0.180 g of CeF.sub.3 were mixed in an alumina mortar, and
the mixture was filled in a molybdenum crucible having a diameter
of 20 mm, and after covering with a molybdenum foil, the crucible
was set in an atmosphere firing electric furnace. After vacuuming
from room temperature to 300.degree. C., 4% hydrogen-containing
nitrogen gas was introduced to ordinary pressure, and the
temperature was raised to 1,500.degree. C. and maintained at
1,500.degree. C. for 12 hours, followed by cooling to take out a
fired product.
[0333] The obtained fired product was pulverized in an alumina
mortar, and the obtained powder was put in 1 mol/L hydrochloric
acid and stirred. The mixture was left to stand still for 1 day and
night, and then, the supernatant was removed, followed by washing
with water and drying to obtain a phosphor. The production
conditions and the evaluation results of properties (emission
properties, absorption efficiency, object color, etc.) of this
phosphor are shown in Tables 12-5 and 12-6.
Examples A14 to A17 and Comparative Example A1
[0334] Phosphors were obtained in the same manner as in Example A13
except that the composition of the alloy and the blend composition
were changed as follows.
TABLE-US-00014 TABLE 12-3 Alloy compositional ratio (La:Ce:Gd:Si)
Blend amounts La Ce Gd Si Alloy Si.sub.3N.sub.4 CeF.sub.3 LaF.sub.3
Comp 2.7 0.3 0 3 2.344 0.655 0 0 Ex. A1 Ex. A14 2.7 0.3 0 3 2.344
0.656 0 0.179 Ex. A15 2.7 0.3 0 3 2.345 0.656 0.180 0 Ex. A16 2.6
0.1 0.3 3 2.349 0.650 0 0.180 Ex. A17 2.4 0.3 0.3 3 2.349 0.651 0
0.180
[0335] The production conditions and the evaluation results of
properties (emission properties, absorption efficiency, object
color, etc.) of the phosphors are shown in Tables 12-5 and 12-6.
The phosphor in Comparative Example A1 had no fluoride added, and
therefore, the luminance was low, and the chroma was also
small.
[0336] By changing the amount of Ce in the raw materials as in
Examples A14 and A15, it is possible to change the emission color
(chromaticity coordinates). By incorporation Ge to the alloy as in
Examples A16 and A17, it is possible to change the emission
color.
Example A18
[0337] La metal, Ce metal and Si metal were mixed so that the ratio
of La:Ce;Si became 4.05:0.45:5.5 and melted by means of an arc
melting method in an argon atmosphere to obtain a LaSi alloy. This
alloy was pulverized by an alumina mortar in a glove box with a
nitrogen atmosphere and passed through a nylon mesh having an
aperture of 25 .mu.m.
[0338] In a glove box containing nitrogen as an operation
atmosphere, 2.481 g of such an alloy powder, 0.520 g of
.alpha.-silicon nitride (SN-E10 manufactured by Ube Industries,
Ltd.) and 0.180 g of LaF.sub.3 were mixed in an alumina mortar, and
the mixture was filled in a molybdenum crucible having a diameter
of 20 mm, and after covering with a molybdenum foil, the crucible
was set in an atmosphere firing electric furnace. After vacuuming
from room temperature to 300.degree. C., 4% hydrogen-containing
nitrogen gas was introduced to ordinary pressure, and the
temperature was raised to 1,500.degree. C. and maintained at
1,500.degree. C. for 12 hours, followed by cooling to take out a
fired product.
[0339] The obtained fired product was pulverized in an alumina
mortar, and the obtained powder was put in 1 mol/L hydrochloric
acid and stirred. The mixture was left to stand still for 1 day and
night, and then, the supernatant was removed, followed by washing
with water and drying to obtain a phosphor.
[0340] The production conditions and the evaluation results of
properties (emission properties, absorption efficiency, object
color, etc.) of this phosphor are shown in Tables 12-5 and
12-6.
Examples A19 to A22
[0341] Phosphors were obtained by treatment in the same manner as
in Example A18 except that the composition of the alloy and the
blend composition were changed as follows.
TABLE-US-00015 TABLE 12-4 Alloy compositional ratio (La:Ce:Si)
Blend amounts (g) La Ce Si Alloy Si.sub.3N.sub.4 LaF.sub.3 Ex. A19
2.7 0.3 3 2.344 0.656 0.18 Ex. A20 4.5 0.5 4 2.226 0.774 0.18 Ex.
A21 2.7 0.3 2 2.150 0.85 0.18 Ex. A22 4.5 0.5 3 2.112 0.888
0.18
[0342] The production conditions and the evaluation results of
properties (emission properties, absorption efficiency, object
color, etc.) of these phosphors are shown in Tables 12-5 and
12-6.
[0343] Phosphors in Examples A18 to A22 are ones prepared from raw
materials obtained by mixing an alloy having a different ratio of
(La+Ce) and Si, and Si.sub.3N.sub.4 to obtain the desired phosphor
composition, and further mixing a fluoride flux. It was found that
even by using such raw materials, it was possible to prepare a
(La,Ce).sub.3Si.sub.6N.sub.11 phosphor.
Example A23
[0344] La metal and Si metal were mixed and melted by means of an
arc melting method in an argon atmosphere to obtain a LaSi alloy.
This alloy was pulverized by an alumina mortar in a glove box with
a nitrogen atmosphere and passed through a nylon mesh having an
aperture of 37 .mu.m.
[0345] In a glove box containing nitrogen as an operation
atmosphere, 2.344 g of such an alloy powder, 0.656 g of
.alpha.-silicon nitride (SN-E10 manufactured by Ube Industries,
Ltd.) and 0.180 g of CeF.sub.3 were mixed in an alumina mortar, and
the mixture was filled in a molybdenum crucible having a diameter
of 20 mm, and after covering with a molybdenum foil, the crucible
was set in an atmosphere firing electric furnace. After vacuuming
from room temperature to 300.degree. C., 4% hydrogen-containing
nitrogen gas was introduced to ordinary pressure, and the
temperature was raised to 1,500.degree. C. and maintained at
1,500.degree. C. for 36 hours, followed by cooling to take out a
fired product.
[0346] The obtained fired product was pulverized in an alumina
mortar, and the obtained powder was put in 1 mol/L hydrochloric
acid and stirred. The mixture was left to stand still for 1 day and
night, and then, the supernatant was removed, followed by washing
with water and drying to obtain a phosphor.
Example A24
[0347] In the procedure of Example A23, the heating temperature and
time were changed to 1,550.degree. C. for 12 hours, to obtain a
phosphor.
TABLE-US-00016 TABLE 12-5 Production conditions Firing Retention
Additives (in the bracket, molar temperature time Pulverization
Alloy composition ratio to La.sub.3Si.sub.6N.sub.11 is indicated)
(.degree. C.) (hr) Ex. A1 Jet mill 7 .mu.m LaSi CeF3(0.2) 1500 12
Ex. A2 Jet mill 7 .mu.m LaSi CeF3(0.2) + YH3(0.4) 1500 12 Ex. A3
Jet mill 7 .mu.m LaSi CeF3(0.2) + YH3(0.2) + YF3(0.2) 1500 12 Ex.
A4 Jet mill 7 .mu.m LaSi CeF3(0.2) + YH3(0.2) 1500 12 Ex. A5 Jet
mill 7 .mu.m LaSi CeF3(0.2) + YH3(0.2) + YF3(0.2) 1500 12 Ex. A6
Jet mill 7 .mu.m LaSi CeF3(0.2) + YH3(0.2) + YF3(0.2) 1500 12 Ex.
A7 Aperture 25 .mu.m LaSi CeF3(0.2) 1500 12 Ex. A8 Jet mill 10
.mu.m LaSi CeF3(0.2) 1500 12 Ex. A9 Jet mill 10 .mu.m LaSi
CeF3(0.2) 1500 12 Ex. A10 Jet mill 11 .mu.m LaSi CeF3(0.2) 1500 12
Ex. A11 Aperture 37 .mu.m (La0.84Ce0.06Y0.1)Si CeF3(0.2) 1500 12
Ex. A12 Jet mill 12 .mu.m (La0.84Ce0.06Y0.1)Si CeF3(0.2) 1500 12
Ex. A13 Aperture 25 .mu.m (La2.9Ce0.1)Si3 CeF3(0.2) 1500 12 Comp.
Ex. A1 Aperture 25 .mu.m (La2.7Ce0.3)Si3 Nil 1500 12 Ex. A14
Aperture 25 .mu.m (La2.7Ce0.3)Si3 LaF3(0.2) 1500 12 Ex. A15
Aperture 25 .mu.m (La2.7Ce0.3)Si3 CeF3(0.2) 1500 12 Ex. A16
Aperture 25 .mu.m (La2.6Ce0.1Gd0.3)Si3 LaF3(0.2) 1500 12 Ex. A17
Aperture 25 .mu.m (La2.4Ce0.3Gd0.3)Si3 LaF3(0.2) 1500 12 Ex. A18
Aperture 25 .mu.m (La4.05Ce0.45)Si5.5 LaF3(0.2) 1500 12 Ex. A19
Aperture 25 .mu.m (La2.7Ce0.3)Si3 LaF3(0.2) 1500 12 Ex. A20
Aperture 25 .mu.m (La4.5Ce0.5)Si4 LaF3(0.2) 1500 12 Ex. A21
Aperture 25 .mu.m (La2.7Ce0.3)Si2 LaF3(0.2) 1500 12 Ex. A22
Aperture 25 .mu.m (La4.5Ce0.5)Si3 LaF3(0.2) 1500 12 Ex. A23
Aperture 37 .mu.m LaSi CeF3(0.2) 1500 36 Ex. A24 Aperture 37 .mu.m
LaSi CeF3(0.2) 1550 12
TABLE-US-00017 TABLE 12-6 Properties of phosphor Emission Emission
peak Chromaticity Chromaticity peak Internal Absorption External
wavelength coordinate coordinate Luminance intensity quantum
efficiency quantum Reflectance (nm) value x value y (%) (%) yield
(%) (%) yield (%) (770 nm) Ex. A1 531 0.414 0.557 137 146 74.6 91.6
68.3 87.3 Ex. A2 538 0.431 0.544 110 112 65.3 88.3 57.7 85.6 Ex. A3
545 0.443 0.538 117 122 66.5 92.2 61.3 84.1 Ex. A4 537 0.426 0.548
120 123 67.2 91.0 61.1 85.8 Ex. A5 545 0.446 0.534 87 89 52.0 88.9
46.3 77.0 Ex. A6 541 0.445 0.538 123 130 68.2 93.1 63.5 78.0 Ex. A7
535 0.427 0.551 128 134 67.3 94.4 63.5 80.5 Ex. A8 533 0.420 0.552
103 107 55.1 89.8 49.4 84.1 Ex. A9 532 0.418 0.555 136 144 66.5
94.4 62.8 84.0 Ex. A10 533 0.417 0.555 131 138 66.5 93.7 62.4 83.7
Ex. A11 537 0.433 0.545 109 114 56.9 92.7 52.8 71.1 Ex. A12 540
0.433 0.544 111 116 56.9 92.6 52.6 72.6 Ex. A13 533 0.420 0.554 124
131 67.7 91.0 61.6 82.8 Comp. 533 0.421 0.549 78 80 41.5 89.6 37.2
64.2 Ex. A1 Ex. A14 534 0.423 0.553 124 131 67.7 92.1 62.4 82.2 Ex.
A15 537 0.434 0.546 118 123 64.2 93.5 60.0 81.5 Ex. A16 537 0.426
0.549 103 109 62.1 87.6 54.4 74.3 Ex. A17 542 0.442 0.540 107 113
59.6 92.3 55.0 72.6 Ex. A18 536 0.421 0.553 129 135 68.6 92.9 63.8
83.5 Ex. A19 533 0.423 0.553 122 127 63.5 93.3 59.2 77.8 Ex. A20
535 0.422 0.552 121 127 64.8 92.5 59.9 80.5 Ex. A21 536 0.423 0.551
118 122 62.8 92.8 58.3 80.1 Ex. A22 534 0.424 0.551 122 126 64.4
93.1 59.9 81.5 Ex. A23 533 0.419 0.555 132 141 70.2 92.7 65.1 83.1
Ex. A24 533 0.415 0.556 126 134 72.5 88.9 64.5 85.6 Object color
Luminosity L* a* b* Chroma (a*.sup.2 + b*.sup.2).sup.0.5 Ex. A1
99.43 -19.39 81.25 83.5 Ex. A2 96.17 -13.12 75.14 76.3 Ex. A3 97.2
-12.89 85.96 86.9 Ex. A4 96.77 -14.68 78.87 80.2 Ex. A5 91.97 -8.51
79.97 71.5 Ex. A6 96.41 -13.34 90.63 91.6 Ex. A7 96.91 -16.54 94.37
95.8 Ex. A8 93.97 -13.53 73.32 74.6 Ex. A9 99.11 -19.03 89.4 91.4
Ex. A10 97.96 -18.76 86.88 88.9 Ex. A11 92.55 -15.33 79.34 80.8 Ex.
A12 92.97 -15.15 77 78.5 Ex. A13 98.16 -18.45 81.78 83.8 Comp. Ex.
A1 82.49 -10.78 60.54 61.5 Ex. A14 97.32 -17.87 87.02 88.8 Ex. A15
95.73 -13.97 90.02 91.1 Ex. A16 94.67 -17.12 72.87 74.9 Ex. A17
92.33 -13.51 85.07 86.1 Ex. A18 97.03 -18.09 84.76 86.7 Ex. A19
94.72 -17.32 86.04 87.8 Ex. A20 96.23 -17.46 83.89 85.7 Ex. A21
85.69 -17.25 81.5 83.3 Ex. A22 96.08 -16.63 84.88 86.5 Ex. A23
98.15 -19.07 89.43 91.4 Ex. A24 98.85 -19.08 77.99 80.3
Examples 37 to 40
Production of Phosphor (LSCN)
[0348] A phosphor powder (LCSN) was obtained by carrying out an
experiment in the same manner as in Example 19 except that in
Example 19, the flux was changed to 6 wt % of MgF.sub.2 and 6 wt %
of CeF.sub.3, and as a treatment after the firing,
stirring/cleaning with 5N hydrochloric acid was added after the
stirring/cleaning with the 10% NH.sub.4HF.sub.2 aqueous solution.
The emission properties of this phosphor under excitation with 455
nm were such that the chromaticity coordinate value x was 0.451,
the value y was 0.533, the emission peak wavelength was 546 nm, and
the luminance to P46-Y3 was 113%.
Production of Light-Emitting Device
[0349] A white light-emitting device was prepared by combining the
obtained phosphor (LCSN) and a short wavelength blue-emitting GAN
type LED chip (ES-CEDBV15 manufactured by Epistar). Here, in order
to disperse and seal the above phosphor powder, a sealing material
silicone resin (SCR-1011 manufactured by Shin-Etsu Chemical Co.,
Ltd.) and a dispersant (REOLOSIL QS-30 manufactured by Tokuyama
Corporation) were used. A phosphor composition was prepared by
adjusting the weight ratio of the phosphor (LCSN):the sealing
material (SCR1011):the dispersant (QS30) to be w:100:2, wherein w
was as shown in Table 13. Such a mixture was heated at 70.degree.
C. for 1 hour and then heated at 150.degree. C. for 5 hours for
curing to form a phosphor-containing portion thereby to obtain a
surface-mounted type white light-emitting device.
Emission Properties
[0350] The spectrum characteristics of the obtained light-emitting
device are shown in Table 13. As shown by the chromaticity
coordinate values x and y in Table 13, it is evident that white
emission can easily be realized by only one type of this phosphor.
In the case of white light of (x,y)=(0.330,0.327) in the
light-emitting device in Example 38, the average color rendering
evaluation number Ra was 68.2, and the emission efficiency was 81.5
Lm/W. By changing the filling amount of LCSN, the emission color
can be freely changed from a bluish white color to a yellowish
white color.
TABLE-US-00018 TABLE 13 Mixing amounts of raw materials Amount
Amount of of Ex. LCSN SCR1011 A SCR1011 B QS30 LCSN LED device No.
(w) (g) (g) (g) (g) x y Lumen Ex. 37 3 0.50 0.50 0.02 0.03 0.271
0.225 5.11 Ex. 38 6 0.50 0.50 0.02 0.06 0.330 0.327 5.30 Ex. 39 9
0.50 0.50 0.02 0.09 0.399 0.440 5.93 Ex. 40 12 0.50 0.50 0.02 0.12
0.434 0.486 5.15 Short wavelength blue LED LED device ES-CEDBV15)
Luminous Emission Applied power efficiency voltage .times. (lm/W)
(lm/W) Peak Applied Applied current Ex. (lumen/ (lumen/ wavelength
W1 voltage current W2 No. W1) W2) Ra (nm) (mW) (V) (mA) (mW) Ex. 37
238 77.5 69.8 441 21.48 3.30 20.0 66.0 Ex. 38 319 81.5 68.2 442
16.59 3.30 19.7 65.0 Ex. 39 388 92.5 60.9 443 15.29 3.34 19.2 64.1
Ex. 40 417 80.7 59.4 443 12.36 3.34 19.1 63.8
Examples 41 to 44
Production of Phosphor
[0351] A phosphor powder (LCSN) was obtained in the same manner as
in Examples 37 to 40.
Production of Light-Emitting Device
[0352] A white light-emitting device was prepared by combining the
obtained phosphor (LCSN) and a long wavelength blue-emitting GAN
type LED chip (NL8436W manufactured by Showa Denko). Here, in order
to disperse and seal the above phosphor powder, a sealing material
silicone resin (SCR-1011 manufactured by Shin-Etsu Chemical Co.,
Ltd.) and a dispersant (REOLOSIL QS-30 manufactured by Tokuyama
Corporation) were used. A phosphor composition was prepared by
adjusting the weight ratio of the phosphor (LCSN):the sealing
material (SCR1011):the dispersant (QS30) to be w:100:2, wherein w
was as shown in Table 14. Such a mixture was heated at 70.degree.
C. for 1 hour and then heated at 150.degree. C. for 5 hours for
curing to form a phosphor-containing portion thereby to obtain a
surface-mounted type white light-emitting device.
Emission Properties
[0353] The spectrum characteristics of the obtained white
light-emitting device are shown in Table 14. As shown by the
chromaticity coordinate values x and y in Table 14, it is evident
that white emission can easily be realized by only one type of this
phosphor. Further, the emission color can freely be changed from
bluish white to yellowish white by changing the filling amount of
LSCN. In the case of white light of (x,y)=(0.349, 0.369) in the
light-emitting device in Example 42, the average color rendering
evaluation number Ra was 68.3, and the emission efficiency was 77.7
Lm/W. When compared with the same emission color, it is evident
that the results in Table 13 using short wavelength blue LED showed
higher emission efficiency than the results in Table 14 using long
wavelength blue LED.
TABLE-US-00019 TABLE 14 Mixing amounts of raw materials Amount
Amount of of Ex. LCSN SCR1011 A SCR1011 B QS30 LCSN LED device No.
(w) (g) (g) (g) (g) x y Lumen Ex. 41 3 0.50 0.50 0.02 0.03 0.267
0.231 4.73 Ex. 42 6 0.50 0.50 0.02 0.06 0.349 0.369 5.19 Ex. 43 9
0.50 0.50 0.02 0.09 0.391 0.430 5.17 Ex. 44 12 0.50 0.50 0.02 0.12
0.421 0.470 5.17 Long wavelength blue LED LED device (NL8436W)
Luminous Emission Applied power efficiency voltage .times. (lm/W)
(lm/W) Peak Applied Applied current Ex. (lumen/ (lumen/ wavelength
W1 voltage current W2 No. W1) W2) Ra (nm) (mW) (V) (mA) (mW) Ex. 41
262 69.1 81.4 451 18.03 3.46 19.8 68.5 Ex. 42 288 77.7 68.3 451
18.02 3.44 19.4 66.7 Ex. 43 293 75.9 63.5 451 17.66 3.46 19.7 68.2
Ex. 44 286 75.8 61.3 451 18.05 3.44 19.8 68.1
Examples 45 to 48
Production of Phosphor (LCSN)
[0354] A phosphor powder (LCSN) was obtained in the same manner as
in Examples 37 to 40.
Production of Red Phosphor (SCASN)
[0355] The respective metals were weighed so that the metal element
compositional ratio became Al:Si=1:1 (molar ratio). Using a
graphite crucible, the raw material metals were melted by means of
a high frequency melting furnace in an argon atmosphere and then
poured from the crucible to a mold and solidified to obtain an
alloy (matrix alloy) wherein the metal element compositional ratio
was Al:Si=1:1.
[0356] The above matrix alloy and other raw material metals were
weighed so that the compositional ratio became
Eu:Sr:Ca:Al:Si:0.008:0.792:0.2:1:1 (molar ratio). The interior of
the furnace was evacuated to 5.times.10.sup.-2 Pa, then the
evacuation was stopped, and argon was filled in the furnace to a
prescribed pressure. In this furnace, the matrix alloy was melted
in a calcia crucible, then Sr was melted, and the melt was poured
from the crucible into a mold and solidified to obtain a raw
material alloy for a phosphor.
[0357] The raw material alloy for a phosphor thus obtained was
roughly pulverized by an alumina mortar in a nitrogen atmosphere
and then pulverized by means of a supersonic jet pulverizer in a
nitrogen atmosphere under a pulverization pressure of 0.15 MPa at a
raw material supplying rate of 0.8 kg/hr. The obtained alloy powder
was washed with water, classified and dried to obtain a phosphor
powder of Sr.sub.0.792Ca.sub.0.200AlEu.sub.0.008SiN.sub.3
(SCASN).
Production of Light-Emitting Device
[0358] A white light-emitting device was prepared by combining the
obtained phosphor (LCSN) and red phosphor (SCASN), and a long
wavelength-blue-emitting GAN type LED chip (NL8436W manufactured by
Showa Denko). Further, in order to disperse and seal the above
phosphor powder, a sealing material silicone resin (SCR-1011
manufactured by Shin-Etsu Chemical Co., Ltd.) and a dispersant
(REOLOSIL QS-30 manufactured by Tokuyama Corporation) were used. A
phosphor composition was prepared by adjusting the weight ratio of
the phosphor (LCSN):the red phosphor (SCASN):the sealing material
(SCR1011):the dispersant (QS30) to be u:v:100:2, respectively,
wherein u and v are as shown in Table 15. Such a mixture was heated
at 70.degree. C. for 1 hour and then heated at 150.degree. C. for 5
hours for curing to form a phosphor-containing portion thereby to
obtain a surface-mounted type white light-emitting device.
Emission Properties
[0359] The spectrum characteristics of the obtained white
light-emitting device are shown in Table 15. As shown by the
chromaticity coordinate values x and y in Table 15, it is evident
that a white emission having a warm white color or light bulb color
can easily be realized. In the case of a warm white light of
(x,y)=(0.410,0.395) in the light-emitting device in Example 45, the
average color rendering evaluation number Ra was 72.2. When
compared with the same emission color to a combination of the long
wavelength blue LED with only LCSN in the light-emitting device in
Example 43, e.g. Ra63.5(x,y)=(0.391, 0.430) in the light-emitting
device in Example 43, it is evident that the color rendering
property is higher when the red phosphor SCASN is combined.
TABLE-US-00020 TABLE 15 LED device Mixing amounts of raw materials
Luminous Emission Amount Amount Amount Amount power efficiency of
of of of (lm/W) (lm/W) Ex. LCSN SCASN SCR1011 A SCR1011 B QS30 LCSN
SCASN (lumen/ (lumen/ No. (u) (v) (g) (g) (g) (g) (g) x y Lumen W1)
W2) Ra Ex. 45 6 1 0.50 0.50 0.2 0.06 0.01 0.410 0.395 4.78 271 70.5
72.2 Ex. 46 3 3 0.50 0.50 0.2 0.03 0.03 0.444 0.335 4.25 226 61.7
71.4 Ex. 47 6 2 0.50 0.50 0.2 0.06 0.02 0.459 0.401 4.75 273 73.2
72.1 Ex. 48 6 3 0.50 0.50 0.2 0.06 0.03 0.478 0.399 4.27 244 64.4
70.3 Long wavelength blue LED (NL8436W) Applied voltage .times. Ex.
Peak wavelength Applied voltage Applied current current W2 No. (nm)
W1 (mW) (V) (mA) (mW) Ex. 45 451 17.65 3.46 19.6 67.8 Ex. 46 451
18.79 3.46 19.9 68.9 Ex. 47 451 17.43 3.38 19.2 64.9 Ex. 48 451
17.49 3.42 19.4 66.3
Examples 49 to 54
Production of Phosphor (LCSN)
[0360] A phosphor powder (LCSN) was obtained in the same manner as
in Examples 37 to 40.
Production of Blue Phosphor (BAM)
[0361] 0.7 mol of barium carbonate (BaCO.sub.3), 0.15 mol of
europium oxide (Eu.sub.2O.sub.3), 1 mol (as Mg) of basic magnesium
carbonate (mass per 1 mol of Mg:93.17) and 5 mol of .alpha.-alumina
(Al.sub.2O.sub.3) were weighed so that the composition of the
respective raw materials charged for a phosphor would be
Ba.sub.0.7Eu.sub.0.3MgAl.sub.10O.sub.17, mixed for 30 minutes in a
mortar and filled in an alumina crucible. This mixture was fired in
a box type firing furnace at 1,200.degree. C. for 5 hours while
supplying nitrogen, and after cooling, the fired product was taken
out from the crucible and pulverized to obtain a precursor for a
phosphor. To this precursor, 0.3 wt % of AlF.sub.3 was added, then
pulverized and mixed in a mortar for 30 minutes, then filled in an
alumina crucible and fired by a box type atmosphere firing furnace
at 1,450.degree. C. for 3 hours in a nitrogen gas containing 4 wt %
of hydrogen, and after cooling, the obtained fired product was
pulverized to obtain a pale blue powder.
[0362] To this powder, 0.42 wt % of AlF.sub.3 was added, then
pulverized and mixed for 30 minutes in a mortar, then filled in an
alumina crucible, and by setting graphite in the beads form in a
space around the crucible, fired at 1,550.degree. C. for 5 hours by
supplying nitrogen to the box type firing furnace at a rate of 4
liters per minute. The obtained fired product was pulverized for 6
hours in a ball mill, then classified and subjected to water
washing treatment to obtain a blue phosphor powder (BAM). The
obtained blue phosphor (BAM) had an emission peak wavelength of 455
nm and an emission peak full width at half maximum of 51 nm.
Production of Light-Emitting Device
[0363] A white light-emitting device was prepared by combining the
obtained phosphor (LCSN) and blue phosphor (BAM), and a near
ultraviolet light-emitting GAN type LED chip (C395 MB290
manufactured by Cree). Here, in order to disperse and seal the
above phosphor powder, a sealing material silicone resin (U111
manufactured by Mitsubishi Chemical Corporation) and a dispersant
(Aerosil RX200 manufactured by Nippon Aerosil Co., Ltd.) were used.
A phosphor composition was prepared by adjusting the weight ratio
of the blue phosphor (BAN):the phosphor (LCSN):the sealing material
(U111):the dispersant (RX200) to be p:q:100:15, wherein p and q are
as shown in Table 16. Such a mixture was heated at 70.degree. C.
for 1 hour and then heated at 150.degree. C. for 5 hours for curing
to form a phosphor-containing portion thereby to obtain a
surface-mounted type white light-emitting device.
Emission Properties
[0364] The spectrum characteristics of the obtained white
light-emitting device are shown in Table 16. As shown by the
chromaticity coordinate values x and y in Table 16, it is evident
that a high color rendering white emission from bluish white to
yellowish white can easily be realized. In the case of white light
of (x,y)=(0.321,0.361) in the light-emitting device in Example 52,
the average color rendering evaluation number Ra was high at 78.3.
As compared to a light-emitting device with a combination of the
long wavelength blue LED with only LCSN in Example 42 having the
same emission color, Ra is of a value exceeding 68.3, and it is
evident that the color rendering property is improved.
TABLE-US-00021 TABLE 16 LED device Mixing amounts of raw materials
Luminous Emission Amount Amount power efficiency Amount of Amount
of (lm/W) (lm/W) Ex. of BAM LCSN U111 RX200 of BAM LCSN (lumen/
(lumen/ No. (p) (q) (g) (g) (g) (g) x y Lumen W1) W2) Ra Ex. 49 9 3
1.00 0.15 0.09 0.03 0.278 0.311 1.78 272 24.9 82.4 Ex. 50 9 6 1.00
0.15 0.09 0.06 0.294 0.329 1.70 264 22.6 81.7 Ex. 51 9 9 1.00 0.15
0.09 0.09 0.317 0.366 1.46 221 19.4 79.5 Ex. 52 9 12 1.00 0.15 0.09
0.12 0.321 0.361 1.73 266 24.3 78.3 Ex. 53 12 8 1.00 0.15 0.12 0.08
0.417 0.492 1.76 271 24.5 64.8 Ex. 54 15 10 1.00 0.15 0.15 0.10
0.429 0.488 1.40 211 19.3 64.8 Near ultraviolet LED (C395MB290)
Applied voltage .times. Ex. Peak wavelength Applied voltage Applied
current current W2 No. (nm) W1 (mW) (V) (mA) (mW) Ex. 49 400 6.53
3.74 19.1 71.4 Ex. 50 400 6.44 3.76 20.0 75.2 Ex. 51 400 6.61 3.76
20.0 75.2 Ex. 52 400 6.51 3.74 19.1 71.4 Ex. 53 400 6.48 3.74 19.2
71.8 Ex. 54 400 6.64 3.74 19.4 72.6
Examples 55 to 58
Production of Phosphor (LCSN)
[0365] A phosphor powder (LCSN) was obtained in the same manner as
in Examples 37 to 40.
Production of Blue Phosphor (BAM)
[0366] A blue phosphor powder (BAM) was obtained in the same manner
as in Examples 49 to 54.
Production of Red Phosphor (CASON)
[0367] Ca.sub.3N.sub.2 (manufactured by CERAC, 200 mesh pass), AlN
(Grade F manufactured Tokuyama Corporation), Si.sub.3N.sub.4
(SN-E10 manufactured Ube Industries, Ltd.) and Eu.sub.2O.sub.3
(manufactured by Shin-Etsu Chemical Co., Ltd.) were weighed so that
the molar ratio would be Eu:Ca:Al:Si=0.008:0.992:1:1.14 by an
electrobalance in a glove box filled with nitrogen with an oxygen
concentration of not more than 1 ppm. In this glove box, all of
these phosphor raw materials were pulverized and mixed for 20
minutes in an alumina mortar until the mixture became uniform. The
obtained raw material mixture was filled in a boron nitride
crucible and fired at 1,800.degree. C. for 2 hours under a nitrogen
pressure of 0.5 MPa. Cleaning, dispersion and classification were
carried out to obtain a red phosphor powder (CASON) having a weight
median diameter (D.sub.50) of 8 .mu.m to 10 .mu.m. The composition
of the obtained phosphor was
Ca.sub.0.992Eu.sub.0.008AlSi.sub.1.14N.sub.3.18O.sub.0.01 by the
charged composition, the emission peak wavelength was 650 nm, and
the full width at half maximum was 92 nm.
Production of Light-Emitting Device
[0368] A white light-emitting device was prepared by combining the
obtained phosphor (LCSN), blue phosphor (BAM) and red phosphor
(CASON), and a near ultraviolet light-emitting GAN type LED chip
(C395MB290 manufactured by Cree). Here, in order to disperse and
seal the above phosphor powder, a sealing material silicone resin
(U111 manufactured by Mitsubishi Chemical Corporation) and a
dispersant (Aerosil RX200 manufactured by Nippon Aerosil Co., Ltd.)
were used. A phosphor composition was prepared by adjusting the
weight ratio of the blue phosphor (BAN):the phosphor (LCSN):the red
phosphor (CASON):the sealing material (U111):the dispersant (RX200)
to be r:s:t:100:15, wherein r, s and t are as shown in Table 17.
Such a mixture was heated at 70.degree. C. for 1 hour and then
heated at 150.degree. C. for 5 hours for curing to form a
phosphor-containing portion thereby to obtain a surface-mounted
type white light-emitting device.
Emission Properties
[0369] The spectrum characteristics of the obtained white
light-emitting device are shown in Table 17. As shown by the
chromaticity coordinate values x and y in Table 17, it is evident
that a high color rendering warm white or light bulb color emission
can easily be realized. In the case of warm white light of
(x,y)=(0.408, 0.417) in the light-emitting device in Example 55,
the average color rendering evaluation number Ra was 77.1. As
compared to the light-emitting device with a combination where no
CASON was added in Example 53 having a similar emission color, Ra
is of a value exceeding 64.8, and it is evident that the color
rendering property is improved.
TABLE-US-00022 TABLE 17 LED device Mixing amounts of raw materials
Luminous Emission Amount Amount Amount Amount power efficiency
Amount of of Amount of of (lm/W) (lm/W) Ex. of BAM LCSN CASON U111
RX200 of BAM LCSN CASON (lumen/ (lumen/ No. (r) (s) (t) (g) (g) (g)
(g) (g) x y Lumen W1) W2) Ra Ex. 55 9 9 1 1.00 0.15 0.09 0.09 0.01
0.408 0.417 1.82 279 24.5 77.1 Ex. 56 15 6 1 1.00 1.15 0.15 0.06
0.01 0.448 0.458 1.59 249 21.9 71.4 Ex. 57 9 3 3 1.00 0.15 0.09
0.03 0.03 0.465 0.363 1.55 232 21.4 74.4 Ex. 58 9 6 3 1.00 0.15
0.09 0.06 0.03 0.469 0.368 1.46 218 19.4 74.4 Near ultraviolet LED
(C395MB290) Applied voltage .times. Ex. Peak wavelength Applied
voltage Applied current current W2 No. (nm) W1 (mW) (V) (mA) (mW)
Ex. 55 400 6.53 3.76 19.8 74.4 Ex. 56 400 6.38 3.74 19.4 72.6 Ex.
57 400 6.68 3.74 19.3 72.2 Ex. 58 400 6.72 3.76 20.0 75.2
Examples 59 and 60
Production of Phosphor (LCSN)
[0370] A phosphor powder (LCSN) was obtained in the same manner as
in Examples 37 to 40.
Production of Blue Phosphor (BAM)
[0371] A blue phosphor powder (BAM) was obtained in the same manner
as in Examples 49 to 54.
Production of Green Phosphor (BSON)
[0372] As raw material compounds, BaCO.sub.3 (267 g), SiO.sub.2
(136 g) and Eu.sub.2O.sub.3 (26.5 g) were sufficiently stirred and
mixed so that the composition of respective raw materials charged
for a phosphor would be
Ba.sub.2.7Eu.sub.0.3Si.sub.6.9O.sub.12N.sub.3.2 and then filled in
an alumina mortar. This mixture was placed in a resistance-heating
system electric furnace provided with a temperature controller,
then heated at a temperature raising rate of 5.degree. C./min to
1,100.degree. C. under atmospheric pressure and held at that
temperature for 5 hours and then left to cool to room temperature.
The obtained sample was pulverized in an alumina mortar to at most
100 .mu.m.
[0373] The sample (295 g) obtained as described above and
Si.sub.3N.sub.4 (45 g) as a raw material compound were sufficiently
stirred and mixed, and then, for the first firing, filled in an
alumina crucible. This mixture was heated to 1,200.degree. C. under
atmospheric pressure, while supplying a mixed gas of 96 vol % of
nitrogen and 4 vol % of hydrogen at a rate of 0.5 L/min and
maintained at that temperature for 5 hours, and then left to cool
to room temperature. The obtained fired powder was pulverized in an
alumina mortar to at most 100 .mu.m.
[0374] 300 g of the fired powder obtained by the above first
firing, BaF.sub.2 (6 g) as a flux and BaHPO.sub.4 (6 g) were
sufficiently stirred and mixed, then filled in an alumina mortar,
and then, as the second firing, heated to 1,350.degree. C. under
atmospheric pressure while supplying a mixed gas of 96 vol % of
nitrogen and 4 vol % of hydrogen at a rate of 0.5 L/min and held at
that temperature for 8 hours, and then left to cool to room
temperature. The obtained fired powder was pulverized in an alumina
mortar to at most 100 .mu.m.
[0375] The sample (70 g) obtained by the above second firing,
BaCl.sub.2 (5.6 g) as a flux and BaHP.sub.4 (3.5 g) were
sufficiently stirred and mixed, then filled in an alumina mortar,
and then, as the third firing, heated to 1,200.degree. C. under
atmospheric pressure, while supplying a mixed gas of 96 vol % of
nitrogen and 4 vol % of hydrogen at a rate of 0.5 L/min and held at
that temperature for 5 hours, and then left to cool to room
temperature. The obtained fired powder was slurried and dispersed
by means of glass beads, then sieved to at most 100 .mu.m, followed
by cleaning treatment, and then, by using a calcium solution and a
phosphate solution, surface coating with a calcium phosphate was
carried out.
[0376] 2 g of the obtained phosphor was heated to 700.degree. C. in
about 40 minutes in atmospheric air by means of a quartz container
having a diameter of 30 mm and held at 700.degree. C. for 10
minutes, whereupon the quartz container was taken out from the
furnace and cooled to room temperature on a heat resistant brick to
obtain a green phosphor powder (BSON).
Production of Red Phosphor (CASON)
[0377] A red phosphor powder (CASON) was obtained in the same
manner as in Examples 55 to 58.
Production of Light-Emitting Device
[0378] A white light-emitting device was prepared by combining the
obtained phosphor (LCSN), blue phosphor (BAM), green phosphor
(BSON), and red phosphor (CASON), and a near ultraviolet
light-emitting GAN type LED chip (C395 MB290 manufactured by Cree).
Here, in order to disperse and seal the above phosphor powder, a
sealing material silicone resin (U111 manufactured by Mitsubishi
Chemical Corporation) and a dispersant (Aerosil RX200 manufactured
by Nippon Aerosil Co., Ltd.) were used. A phosphor composition was
prepared by adjusting the weight ratio of the blue phosphor
(BAN):the green phosphor (BSON):the phosphor (LCSN):the red
phosphor (CASON):the sealing material (U111):the dispersant (RX200)
to be h:k:l:m:100:2, wherein h, k, l and m are as shown in Table
18. Such a mixture was heated at 70.degree. C. for 1 hour and then
heated at 150.degree. C. for 5 hours for curing to form a
phosphor-containing portion thereby to obtain a surface-mounted
type white light-emitting device.
Emission Properties
[0379] The spectrum characteristics of the obtained white
light-emitting device are shown in Table 18. As shown by the
chromaticity coordinate values x and y in Table 18, it is evident
that a high color rendering warm white or light bulb white emission
can easily be realized. In the case of a light bulb color emission
of (x,y)=(0.442, 0.426) in the light-emitting device in Example 60,
the average color rendering evaluation number Ra was high at 83.1.
As compared to the light-emitting device with a combination where
no BSON was added in Example 56 having a similar emission color, Ra
is of a value exceeding 71.4, and it is evident that the color
rendering property is very much improved.
TABLE-US-00023 TABLE 18 Mixing amounts of raw materials Amount
Amount Amount Amount Amount Amount Amount of of of Amount of of of
Ex. of BAM BSON LCSN CASON U111 RX200 of BAM BSON LCSN CASON No.
(h) (k) (l) (m) (g) (g) (g) (g) (g) (g) Ex. 59 15 1 1 1 1.00 0.15
0.15 0.01 0.01 0.01 Ex. 60 9 6 3 3 1.00 0.15 0.09 0.06 0.03 0.03
LED device Near ultraviolet LED (C395MB290) Luminous Emission
Applied power efficiency voltage .times. (lm/W) (lm/W) Peak Applied
Applied current Ex. (lumen/ (lumen/ wavelength W1 voltage current
W2 No. x y Lumen W1) W2) Ra (nm) (mW) (V) (mA) (mW) Ex. 59 0.411
0.432 2.03 309 28.3 82.2 400 6.55 3.74 19.1 71.4 Ex. 30 0.442 0.426
1.56 241 21.9 83.1 400 6.49 3.74 19.1 71.4
Comparative Example 6
[0380] A LED device disclosed in Example 39 in JP-A-2008-285659 is
presented as Comparative Example 6 in this application. The LED
device in this Comparative Example is one obtained by combining a
phosphor (one obtained by firing a mixture of CaSiN.sub.2 powder,
lanthanum nitride powder, cerium oxide powder, silicon nitride
powder and 0.5 wt % of CaF.sub.2 flux at 2,000.degree. C. for 5
minutes under nitrogen pressure of 0.92 MPa and having a charged
composition of Ca.sub.0.75La.sub.2.4Ce.sub.0.1Si.sub.6N.sub.11) and
a blue-emitting GAN type LED chip (460EZ manufactured by Cree). The
curing conditions are the same as in Example 37. The raw material
mixing amounts, the emission properties, etc. of the light-emitting
device in Comparative Example 6 are shown in Table 19.
[0381] In the light-emitting device in Comparative Example 6, a
white light of (x,y)=(328,313) was obtained, and its luminous power
was 281 Lm/W. The luminous power in the light-emitting device in
Example 38 having a similar emission color is 319 Lm/W, which is
higher than in Comparative Example 6, and it is evident that one
having the phosphor of the present invention mounted on LED is
capable of emitting brighter white light under the same output
condition.
TABLE-US-00024 TABLE 19 LED device Luminous Short Comp. Mixing
amounts of raw power wavelength Ex. materials (weight ratio) (lm/W)
blue LED No. LCSN SCR1011 QS30 x y Lumen (lumen/W1) W1 (mW) Comp. 4
97 3 0.328 0.313 1.57 281 5.58 Ex. 6 Note) Short wavelength blue
LED: 460EZ manufactured by Cree
Example 61
Production of Alloy
[0382] The respective metal raw materials of La solid metal blank,
Ce solid metal blank and Si solid metal blank were weighed so that
the metal element compositional ratio would be La:Ce:Si=2.9:0.1:6
(molar ratio), gently mixed and introduced into an arc melting
furnace (ACM-CO1P manufactured by DIAVAC Limited). After evacuating
the interior of the furnace to 1.times.10.sup.-2 Pa, argon was
introduced, and the mixture was melted by conducting an electric
current of about 100 mA to the raw material metals in an argon
atmosphere. After confirming that the molten metal was sufficiently
rotated by the principle of electromagnetic induction, application
of the current was stopped, and the molten metal was naturally
cooled and solidified to obtain an alloy for a phosphor raw
material. The obtained alloy for a phosphor raw material was
confirmed to be a uniform alloy having the above metal element
compositional ratio by SEM-EDX. By means of an alumina mortar and a
nylon mesh sieve, the alloy for a phosphor raw material was
pulverized to an alloy powder having a particle size of at most 37
.mu.m, which was used as a raw material for nitriding
treatment.
Firing of Raw Material
[0383] In a glove box containing nitrogen as an operation
atmosphere, 1 g of such an alloy powder and 0.06 g of CeF.sub.3 (6
wt % to the alloy raw material) were mixed in an alumina mortar,
and the mixture was pressed on a molybdenum tray having a diameter
of 30 mm and set in an electric furnace with a molybdenum inner
wall having a tungsten heater. After vacuuming from room
temperature to 120.degree. C., 4% hydrogen-containing nitrogen gas
was introduced to ordinary pressure, and while maintaining the
supply rate of 0.5 L/min, the temperature was raised to 800.degree.
C., and then the temperature was raised at 0.5.degree. C./min
within ranges of from 800.degree. C. to 1,250.degree. C. and from
1,350.degree. C. to 1,550.degree. C., and at 0.1.degree. C./min
within a range of from 1,250.degree. C. to 1,350.degree. C., and
then firing was carried out at 1,550.degree. C. for 15 hours,
followed by pulverization in an alumina mortar.
Treatment of Fired Product
[0384] The obtained fired product was pulverized in an agate
mortar, and the obtained powder was stirred and cleaned with a
NH.sub.4HF.sub.2 aqueous solution having a concentration of 10 wt %
for 1 hour, then washed with water, and then stirred and cleaned
with 5N hydrochloric acid for 1 hour and then dried to obtain a
phosphor. The evaluation results of properties (emission properties
and object color) of this phosphor are shown in Table 20. Here, in
Table 20, the luminance (%) and the emission intensity (%) are
relative values to a YAG commercial product (P46-Y3 manufactured by
Kasei Optonix) being 100%.
[0385] The phosphor in Example 61 had a luminance as high as 121%
to P46-Y3; a* and b* representing the object color were -17 and 82,
respectively; and the chroma (a*.sup.2+b*.sup.2).sup.1/2 was very
high at 84. On the other hand, evaluation was carried out without
treatment with the NH.sub.4HF.sub.2 aqueous solution or
hydrochloric acid, whereby the luminance to P46-Y3 was 92%.
Examples 62 to 68
[0386] Experiments were all carried out in the same manner as in
Example 61 except that in Example 61, the composition of the raw
material alloy was changed from La.sub.2.9Ce.sub.0.1Si.sub.6 to the
compositions disclosed in lines for Examples 62 to 68 in Table 20.
The evaluation results of properties (emission properties and
object color) of the obtained phosphors are shown in Table 20.
[0387] With phosphors obtained by using, as the raw material, an
alloy containing e.g. Gd, Y or Sc, or an alloy having the amount of
Ce increased from 0.15 to 0.45, the chromaticity coordinate value x
is increased from 0.425 to 0.431 or 0.458, which indicates
effectiveness to make the emission color to be genuine yellow. Of
these phosphors (Examples 62 to 68), a* and b* are from -8 to -14
and from 73 to 88, respectively, and the chroma
(a*.sup.2+b*.sup.2).sup.1/2 is very high at from 73 to 89, which
indicates that they are phosphors having a good object color.
[0388] The blue emission intensity due to a Ce-activated
LaSi.sub.3N.sub.5 type byproduct slightly included in the phosphors
(Examples 61, 65 and 66) obtained by using, as the raw material,
La.sub.2.9Ce.sub.0.1Si.sub.6,
La.sub.2.75Gd.sub.0.15Ce.sub.0.1Si.sub.6, and
La.sub.2.6Gd.sub.0.3Ce.sub.0.1Si.sub.6, respectively, becomes 9.6%,
5.9% and 5.9%, respectively, as represented by the relative
intensity to the yellow emission intensity of P46-Y3 excited with
455 nm, which indicates that is effective to substantially prevent
blue emission due to the Ce-activated LaSi.sub.3N.sub.5 type.
TABLE-US-00025 TABLE 20 Raw material alloy
La(.sub.3-x-y)A.sub.xB.sub.ySi.sub.6 Firing Emission properties
(455 nm excitation) Metal Metal condition Emission Relative
Emission element A element B Flux peak luminance intensity Ex.
Molar Molar Amount wavelength Chromaticity Chromaticity to P46-Y3
to P46- No. Type ratio x Type ratio y Type (wt %) (nm) coordinate x
coordinate y (%) Y3 (%) Ex. 61 Ce 0.1 -- 0 CeF.sub.3 6 535 0.425
0.551 121 126 Ex. 62 Ce 0.15 -- 0 CeF.sub.3 6 536 0.431 0.547 115
119 Ex. 63 Ce 0.3 -- 0 CeF.sub.3 6 537 0.438 0.543 113 118 Ex. 64
Ce 0.45 -- 0 CeF.sub.3 6 544 0.444 0.539 107 111 Ex. 65 Ce 0.1 Gd
0.15 CeF.sub.3 6 541 0.442 0.540 99 102 Ex. 66 Ce 0.1 Gd 0.3
CeF.sub.3 6 542 0.448 0.536 96 101 Ex. 67 Ce 0.1 Y 0.3 CeF.sub.3 6
545 0.450 0.534 93 98 Ex. 68 Ce 0.1 Sc 0.3 CeF.sub.3 6 547 0.458
0.528 76 80 Object color Ex. Luminosity Chroma No. L* a* b*
(a*.sup.2 + b*.sup.2).sup.0.5 Ex. 61 96 -17 82 84 Ex. 62 93 -14 85
86 Ex. 63 92 -13 88 89 Ex. 64 89 -10 85 86 Ex. 65 88 -12 81 82 Ex.
66 85 -11 78 79 Ex. 67 86 -11 79 80 Ex. 68 78 -8 73 73
[0389] As is apparent from the foregoing results, it has been found
that a light-emitting device using the phosphor of the present
invention is provided with properties which are useful for
practically advantageous applications.
INDUSTRIAL APPLICABILITY
[0390] Uses of the phosphor of the present invention are not
particularly limited, and it is useful in various fields in which a
usual phosphor is employed. However, by utilizing the
characteristic such that it is excellent in the temperature
properties, it is suitable for the purpose of realizing an
illuminant for common illumination to be excited by a light source
such as near ultraviolet LED or blue LED. Further, the
light-emitting device of the present invention employing the
phosphor of the present invention having the above characteristic,
is useful in various fields in which a usual light-emitting device
is employed. However, it is particularly useful as a light source
for an image display device or a lighting device.
[0391] This application is a continuation of PCT Application No.
PCT/JP2010/055934, filed Mar. 31, 2010, which is based upon and
claims the benefit of priority from Japanese Patent Application No.
2009-086840 filed on Mar. 31, 2009 and Japanese Patent Application
No. 2009-236147 filed on Oct. 13, 2009. The contents of those
applications are incorporated herein by reference in its
entirety.
REFERENCE SYMBOLS
[0392] 1: Second illuminant [0393] 2: Surface-emitting GaN type LD
[0394] 3: Substrate [0395] 4: Light-emitting device [0396] 5: Mount
lead [0397] 6: Inner lead [0398] 7: First illuminant [0399] 8:
Phosphor-containing resin portion [0400] 9: Conductive wire [0401]
10: Molded component [0402] 11: Surface-emitting lighting system
[0403] 12: Casing [0404] 13: Light-emitting device [0405] 14:
Diffuser panel [0406] 22: First illuminant [0407] 23: Second
illuminant [0408] 24: Frame [0409] 25: Conductive wire [0410] 26,
27: Electrodes
* * * * *